Discontinuous reception operation with additional wake-up opportunities

ABSTRACT

The disclosure relates to methods for improving the DRX operation of a UE by introducing an additional DRX wake-up cycle, which runs in parallel to the short and/or long DRX cycle. The DRX wake-up cycle defines time intervals after which the UE starts monitoring the PDCCH for a wake-up duration of time; the UE does not perform any other operation during the wake-up duration apart from monitoring the PDCCH. The time intervals of the wake-up cycle between the wake-up durations are preferably shorter than the one of the DRX long cycle, and may have the same or a shorter length than the ones of the DRX short cycle. The wake-up duration may be as long as the on-duration of the DRX short/long cycle, or may be preferably much shorter, such as only one or a few subframes.

BACKGROUND

Technical Field

The disclosure relates to methods for improvements to the discontinuousreception operation of a mobile terminal. The disclosure is alsoproviding the mobile terminal for performing the methods describedherein.

Description of the Related Art

Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving a radioaccess technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies, 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support for the next decade.The ability to provide high bit rates is a key measure for LTE.

The work item (WI) specification on Long-Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial RadioAccess Network (UTRAN) is finalized as Release 8 (LTE Rel. 8). The LTEsystem represents efficient packet-based radio access and radio accessnetworks that provide full IP-based functionalities with low latency andlow cost. In LTE, scalable multiple transmission bandwidths arespecified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order toachieve flexible system deployment using a given spectrum. In thedownlink, Orthogonal Frequency Division Multiplexing (OFDM) based radioaccess was adopted because of its inherent immunity to multipathinterference (MPI) due to a low symbol rate, the use of a cyclic prefix(CP) and its affinity to different transmission bandwidth arrangements.Single-carrier frequency division multiple access (SC-FDMA) based radioaccess was adopted in the uplink, since provisioning of wide areacoverage was prioritized over improvement in the peak data rateconsidering the restricted transmit power of the user equipment (UE).Many key packet radio access techniques are employed includingmultiple-input multiple-output (MIMO) channel transmission techniquesand a highly efficient control signaling structure is achieved in LTERel. 8/9.

LTE Architecture

The overall architecture is shown in FIG. 1 and a more detailedrepresentation of the E-UTRAN architecture is given in FIG. 2. TheE-UTRAN consists of an eNodeB, providing the E-UTRA user plane(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towardsthe user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY),Medium Access Control (MAC), Radio Link Control (RLC), and Packet DataControl Protocol (PDCP) layers that include the functionality ofuser-plane header-compression and encryption. It also offers RadioResource Control (RRC) functionality corresponding to the control plane.It performs many functions including radio resource management,admission control, scheduling, enforcement of negotiated uplink Qualityof Service (QoS), cell information broadcast, ciphering/deciphering ofuser and control plane data, and compression/decompression ofdownlink/uplink user plane packet headers. The eNodeBs areinterconnected with each other by means of the X2 interface.

The eNodeBs are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g., parameters of the IP bearerservice, network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at time of intra-LTEhandover involving Core Network (CN) node relocation. It is responsiblefor authenticating the user (by interacting with the HSS). TheNon-Access Stratum (NAS) signaling terminates at the MME and it is alsoresponsible for generation and allocation of temporary identities touser equipments. It checks the authorization of the user equipment tocamp on the service provider's Public Land Mobile Network (PLMN) andenforces user equipment roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN. TheMME also terminates the S6a interface towards the home HSS for roaminguser equipments.

Component Carrier Structure in LTE (Release 8)

The downlink component carrier of a 3GPP LTE (Release 8) is subdividedin the time-frequency domain in so-called subframes. In 3GPP LTE(Release 8) each subframe is divided into two downlink slots as shown inFIG. 3, wherein the first downlink slot comprises the control channelregion (PDCCH region) within the first OFDM symbols. Each subframeconsists of a give number of OFDM symbols in the time domain (12 or 14OFDM symbols in 3GPP LTE (Release 8)), wherein each OFDM symbol spansover the entire bandwidth of the component carrier. The OFDM symbolsthus each consists of a number of modulation symbols transmitted onrespective N_(RB) ^(DL)×N_(sc) ^(RB) subcarriers as also shown in FIG.4.

Assuming a multi-carrier communication system, e.g., employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”.A physical resource block is defined as N_(symb) ^(DL) consecutive OFDMsymbols in the time domain and N_(sc) ^(RB) consecutive subcarriers inthe frequency domain as exemplified in FIG. 4. In 3GPP LTE (Release 8),a physical resource block thus consists of N_(symb) ^(DL)×N_(sc) ^(RB)resource elements, corresponding to one slot in the time domain and 180kHz in the frequency domain (for further details on the downlinkresource grid, see for example 3GPP TS 36.211, “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 8)”, version 8.9.0 or 9.0.0, section 6.2, available athttp://www.3gpp.org and incorporated herein by reference).

The term “component carrier” refers to a combination of several resourceblocks. In future releases of LTE, the term “component carrier” is nolonger used; instead, the terminology is changed to “cell”, which refersto a combination of downlink and optionally uplink resources. Thelinking between the carrier frequency of the downlink resources and thecarrier frequency of the uplink resources is indicated in the systeminformation transmitted on the downlink resources.

Further Advancements for LTE (LTE-A)

The frequency spectrum for IMT-Advanced was decided at the WorldRadiocommunication Conference 2007 (WRC-07). Although the overallfrequency spectrum for IMT-Advanced was decided, the actual availablefrequency bandwidth is different according to each region or country.Following the decision on the available frequency spectrum outline,however, standardization of a radio interface started in the 3rdGeneration Partnership Project (3GPP). At the 3GPP TSG RAN #39 meeting,the Study Item description on “Further Advancements for E-UTRA(LTE-Advanced)” was approved. The study item covers technologycomponents to be considered for the evolution of E-UTRA, e.g., tofulfill the requirements on IMT-Advanced. Two major technologycomponents are described in the following.

Carrier Aggregation in LTE-A for Support of Wider Bandwidth

The bandwidth that the LTE-Advanced system is able to support is 100MHz, while an LTE system can only support 20 MHz. Nowadays, the lack ofradio spectrum has become a bottleneck of the development of wirelessnetworks, and as a result it is difficult to find a spectrum band whichis wide enough for the LTE-Advanced system. Consequently, it is urgentto find a way to gain a wider radio spectrum band, wherein a possibleanswer is the carrier aggregation functionality.

In carrier aggregation, two or more component carriers (componentcarriers) are aggregated in order to support wider transmissionbandwidths up to 100 MHz. Several cells in the LTE system are aggregatedinto one wider channel in the LTE-Advanced system which is wide enoughfor 100 MHz even though these cells in LTE are in different frequencybands.

All component carriers can be configured to be LTE Rel. 8/9 compatible,at least when the aggregated numbers of component carriers in the uplinkand the downlink are the same. Not all component carriers aggregated bya user equipment may necessarily be Rel. 8/9 compatible. Existingmechanism (e.g., barring) may be used to avoid Rel-8/9 user equipmentsto camp on a component carrier.

A user equipment may simultaneously receive or transmit one or multiplecomponent carriers (corresponding to multiple serving cells) dependingon its capabilities. A LTE-A Rel. 10 user equipment with receptionand/or transmission capabilities for carrier aggregation cansimultaneously receive and/or transmit on multiple serving cells,whereas an LTE Rel. 8/9 user equipment can receive and transmit on asingle serving cell only, provided that the structure of the componentcarrier follows the Rel. 8/9 specifications.

Carrier aggregation is supported for both contiguous and non-contiguouscomponent carriers with each component carrier limited to a maximum of110 Resource Blocks in the frequency domain using the 3GPP LTE (Release8/9) numerology.

It is possible to configure a 3GPP LTE-A (Release 10) compatible userequipment to aggregate a different number of component carriersoriginating from the same eNodeB (base station) and of possiblydifferent bandwidths in the uplink and the downlink. The number ofdownlink component carriers that can be configured depends on thedownlink aggregation capability of the UE. Conversely, the number ofuplink component carriers that can be configured depends on the uplinkaggregation capability of the UE. It may not be possible to configure amobile terminal with more uplink component carriers than downlinkcomponent carriers.

In a typical TDD deployment, the number of component carriers and thebandwidth of each component carrier in uplink and downlink is the same.Component carriers originating from the same eNodeB need not to providethe same coverage.

The spacing between center frequencies of contiguously aggregatedcomponent carriers shall be a multiple of 300 kHz. This is in order tobe compatible with the 100 kHz frequency raster of 3GPP LTE (Release8/9) and at the same time preserve orthogonality of the subcarriers with15 kHz spacing. Depending on the aggregation scenario, the n×300 kHzspacing can be facilitated by insertion of a low number of unusedsubcarriers between contiguous component carriers.

The nature of the aggregation of multiple carriers is only exposed up tothe MAC layer. For both uplink and downlink there is one HARQ entityrequired in MAC for each aggregated component carrier. There is (in theabsence of SU-MIMO for uplink) at most one transport block per componentcarrier. A transport block and its potential HARQ retransmissions needto be mapped on the same component carrier.

The Layer 2 structure with activated carrier aggregation is shown inFIG. 5 and FIG. 6 for the downlink and uplink respectively.

When carrier aggregation is configured, the mobile terminal only has oneRRC connection with the network. At RRC connectionestablishment/re-establishment, one cell provides the security input(one ECGI, one PCI and one ARFCN) and the non-access stratum mobilityinformation (e.g., TAI) similarly as in LTE Rel. 8/9. After RRCconnection establishment/re-establishment, the component carriercorresponding to that cell is referred to as the downlink Primary Cell(PCell). There is always one and only one downlink PCell (DL PCell) andone uplink PCell (UL PCell) configured per user equipment in connectedstate. Within the configured set of component carriers, other cells arereferred to as Secondary Cells (SCells). The characteristics of thedownlink and uplink PCell are:

-   -   The uplink PCell is used for transmission of Layer 1 uplink        control information    -   The downlink PCell cannot be de-activated, unlike SCells    -   Re-establishment is triggered when the downlink PCell        experiences Rayleigh fading (RLF), not when downlink SCells        experience RLF    -   The downlink PCell cell can change with handover    -   Non-access stratum information is taken from the downlink PCell    -   PCell can only be changed with handover procedure (i.e., with        security key change and RACH procedure)    -   PCell is used for transmission of PUCCH

The configuration and reconfiguration of component carriers can beperformed by RRC. Activation and deactivation is done via MAC controlelements. At intra-LTE handover, RRC can also add, remove, orreconfigure SCells for usage in the target cell. When adding a newSCell, dedicated RRC signaling is used for sending the systeminformation of the SCell, the information being necessary fortransmission/reception (similarly as in Rel-8/9 for handover).

When a user equipment is configured with carrier aggregation there isone pair of uplink and downlink component carriers that is alwaysactive. The downlink component carrier of that pair might be alsoreferred to as ‘DL anchor carrier’. Same applies also for the uplink.

When carrier aggregation is configured, a user equipment may bescheduled over multiple component carriers simultaneously but at mostone random access procedure shall be ongoing at any time. Cross-carrierscheduling allows the PDCCH of a component carrier to schedule resourceson another component carrier. For this purpose a component carrieridentification field is introduced in the respective DCI formats, calledCIF.

A linking between uplink and downlink component carriers allowsidentifying the uplink component carrier for which the grant applieswhen there is no-cross-carrier scheduling. The linkage of downlinkcomponent carriers to uplink component carrier does not necessarily needto be one to one. In other words, more than one downlink componentcarrier can link to the same uplink component carrier. At the same time,a downlink component carrier can only link to one uplink componentcarrier.

LTE RRC States

LTE is based on only two main states: “RRC_IDLE” and “RRC_CONNECTED”.

In RRC_IDLE the radio is not active, but an ID is assigned and trackedby the network. More specifically, a mobile terminal in RRC_IDLEperforms cell selection and reselection—in other words, it decides onwhich cell to camp. The cell (re)selection process takes into accountthe priority of each applicable frequency of each applicable RadioAccess Technology (RAT), the radio link quality and the cell status(i.e., whether a cell is barred or reserved). An RRC_IDLE mobileterminal monitors a paging channel to detect incoming calls, and alsoacquires system information. The system information mainly consists ofparameters by which the network (E-UTRAN) can control the cell(re)selection process. RRC specifies the control signaling applicablefor a mobile terminal in RRC_IDLE, namely paging and system information.The mobile terminal behavior in RRC_IDLE is specified in TS 25.912,e.g., Chapter 8.4.2 incorporate herein by reference.

In RRC_CONNECTED the mobile terminal has an active radio operation withcontexts in the eNodeB. The E-UTRAN allocates radio resources to themobile terminal to facilitate the transfer of (unicast) data via shareddata channels. To support this operation, the mobile terminal monitorsan associated control channel which is used to indicate the dynamicallocation of the shared transmission resources in time and frequency.The mobile terminal provides the network with reports of its bufferstatus and of the downlink channel quality, as well as neighboring cellmeasurement information to enable E-UTRAN to select the most appropriatecell for the mobile terminal. These measurement reports include cellsusing other frequencies or RATs. The UE also receives systeminformation, consisting mainly of information required to use thetransmission channels. To extend its battery lifetime, a UE inRRC_CONNECTED may be configured with a Discontinuous Reception (DRX)cycle. RRC is the protocol by which the E-UTRAN controls the UE behaviorin RRC_CONNECTED.

FIG. 7 shows a state diagram with an overview of the relevant functionsperformed by the mobile terminal in IDLE and CONNECTED state.

Layer 1/Layer 2 (L1/L2) Control Signaling

In order to inform the scheduled users about their allocation status,transport format and other data-related information (e.g., HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a subframe,assuming that the user allocation can change from subframe to subframe.It should be noted that user allocation might also be performed on a TTI(Transmission Time Interval) basis, where the TTI length is a multipleof the subframes. The TTI length may be fixed in a service area for allusers, may be different for different users, or may even by dynamic foreach user. Generally, the L1/2 control signaling needs only betransmitted once per TTI.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). A PDCCH carries a message as a Downlink ControlInformation (DCI), which includes resource assignments and other controlinformation for a mobile terminal or groups of UEs. In general, severalPDCCHs can be transmitted in one subframe.

It should be noted that in 3GPP LTE, assignments for uplink datatransmissions, also referred to as uplink scheduling grants or uplinkresource assignments, are also transmitted on the PDCCH.

With respect to scheduling grants, the information sent on the L1/L2control signaling may be separated into the following two categories,Shared Control Information (SCI) carrying Cat 1 information and DownlinkControl Information (DCI) carrying Cat 2/3 information.

Shared Control Information (SCI) Carrying Cat 1 Information

The shared control information part of the L1/L2 control signalingcontains information related to the resource allocation (indication).The shared control information typically contains the followinginformation:

-   -   A user identity indicating the user(s) that is/are allocated the        resources.    -   RB allocation information for indicating the resources (Resource        Blocks (RBs)) on which a user(s) is/are allocated. The number of        allocated resource blocks can be dynamic.    -   The duration of assignment (optional), if an assignment over        multiple subframes (or TTIs) is possible.

Depending on the setup of other channels and the setup of the DownlinkControl Information (DCI)—see below—the shared control information mayadditionally contain information such as ACK/NACK for uplinktransmission, uplink scheduling information, information on the DCI(resource, MCS, etc.).

Downlink Control Information (DCI) Carrying Cat 2/3 Information

The downlink control information part of the L1/L2 control signalingcontains information related to the transmission format (Cat 2information) of the data transmitted to a scheduled user indicated bythe Cat 1 information. Moreover, in case of using (Hybrid) ARQ as aretransmission protocol, the Cat 2 information carries HARQ (Cat 3)information. The downlink control information needs only to be decodedby the user scheduled according to Cat 1. The downlink controlinformation typically contains information on:

-   -   Cat 2 information: Modulation scheme, transport-block (payload)        size or coding rate, MIMO (Multiple Input Multiple        Output)-related information, etc. Either the transport-block (or        payload size) or the code rate can be signaled. In any case        these parameters can be calculated from each other by using the        modulation scheme information and the resource information        (number of allocated resource blocks)    -   Cat 3 information: HARQ related information, e.g., hybrid ARQ        process number, redundancy version, retransmission sequence        number

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in its fields. Thedifferent DCI formats that are currently defined for LTE are as followsand described in detail in 3GPP TS 36.212, “Multiplexing and channelcoding”, section 5.3.3.1 (available at http://www.3gpp.org andincorporated herein by reference).

Format 0: DCI Format 0 is used for the transmission of resource grantsfor the PUSCH.

Format 1: DCI Format 1 is used for the transmission of resourceassignments for single codeword PDSCH transmissions (transmission modes1, 2 and 7).

Format 1A: DCI Format 1A is used for compact signaling of resourceassignments for single codeword PDSCH transmissions, and for allocatinga dedicated preamble signature to a mobile terminal for contention-freerandom access.

Format 1B: DCI Format 1B is used for compact signaling of resourceassignments for PDSCH transmissions using closed loop precoding withrank-1 transmission (transmission mode 6). The information transmittedis the same as in Format 1A, but with the addition of an indicator ofthe precoding vector applied for the PDSCH transmission.

Format 1C: DCI Format 1C is used for very compact transmission of PDSCHassignments. When format 1C is used, the PDSCH transmission isconstrained to using QPSK modulation. This is used, for example, forsignaling paging messages and broadcast system information messages.

Format 1D: DCI Format 1D is used for compact signaling of resourceassignments for PDSCH transmission using multi-user MIMO. Theinformation transmitted is the same as in Format 1B, but instead of oneof the bits of the precoding vector indicators, there is a single bit toindicate whether a power offset is applied to the data symbols. Thisfeature is needed to show whether or not the transmission power isshared between two UEs. Future versions of LTE may extend this to thecase of power sharing between larger numbers of UEs.

Format 2: DCI Format 2 is used for the transmission of resourceassignments for PDSCH for closed-loop MIMO operation.

Format 2A: DCI Format 2A is used for the transmission of resourceassignments for PDSCH for open-loop MIMO operation. The informationtransmitted is the same as for Format 2, except that if the eNodeB hastwo transmit antenna ports, there is no precoding information, and forfour antenna ports two bits are used to indicate the transmission rank.

Format 3 and 3A: DCI formats 3 and 3A are used for the transmission ofpower control commands for PUCCh and PUSCH with 2-bit or 1-bit poweradjustments respectively. These DCI formats contain individual powercontrol commands for a group of UEs.

The following table gives an overview of the available DCI formats.

Number of bits including CRC (for a system bandwidth of 50 DCI RBs andfour format Purpose antennas at eNodeB 0 PUSCH grants 42 1 PDSCHassignments 47 with a single codeword 1A PDSCH assignments 42 using acompact format 1B PDSCH assignments for 46 rank-1 transmission 1C PDSCHassignments using 26 a very compact format 1D PDSCH assignments for 46multi-user MIMO 2 PDSCH assignments for 62 closed-loop MIMO operation 2APDSCH assignments for 58 open-loop MIMO operation 3 Transmit PowerControl (TPC) 42 commands for multiple users for PUCCH and PUSCH with2-bit power adjustments 3A Transmit Power Control (TPC) 42 commands formultiple users for PUCCH and PUSCH with 1-bit power adjustments

For further information regarding the DCI formats and the particularinformation that is transmitted in the DCI, please refer to thetechnical standard or to LTE—The UMTS Long Term Evolution—From Theory toPractice, Edited by Stefanie Sesia, Issam Toufik, Matthew Baker, Chapter9.3, incorporated herein by reference.

Downlink & Uplink Data Transmission

Regarding downlink data transmission, L1/L2 control signaling istransmitted on a separate physical channel (PDCCH), along with thedownlink packet data transmission. This L1/L2 control signalingtypically contains information on:

-   -   The physical resource(s) on which the data is transmitted (e.g.,        subcarriers or subcarrier blocks in case of OFDM, codes in case        of CDMA). This information allows the mobile terminal (receiver)        to identify the resources on which the data is transmitted.    -   When user equipment is configured to have a Carrier Indication        Field (CIF) in the L1/L2 control signaling, this information        identifies the component carrier for which the specific control        signaling information is intended. This enables assignments to        be sent on one component carrier which are intended for another        component carrier (“cross-carrier scheduling”). This other,        cross-scheduled component carrier could be for example a        PDCCH-less component carrier, i.e., the cross-scheduled        component carrier does not carry any L1/L2 control signaling.    -   The Transport Format, which is used for the transmission. This        can be the transport block size of the data (payload size,        information bits size), the MCS (Modulation and Coding Scheme)        level, the Spectral Efficiency, the code rate, etc. This        information (usually together with the resource allocation        (e.g., the number of resource blocks assigned to the user        equipment)) allows the user equipment (receiver) to identify the        information bit size, the modulation scheme and the code rate in        order to start the demodulation, the de-rate-matching and the        decoding process. The modulation scheme may be signaled        explicitly.    -   Hybrid ARQ (HARQ) information:    -   HARQ process number: Allows the user equipment to identify the        hybrid ARQ process on which the data is mapped.    -   Sequence number or new data indicator (NDI): Allows the user        equipment to identify if the transmission is a new packet or a        retransmitted packet. If soft combining is implemented in the        HARQ protocol, the sequence number or new data indicator        together with the HARQ process number enables soft-combining of        the transmissions for a PDU prior to decoding.    -   Redundancy and/or constellation version: Tells the user        equipment, which hybrid ARQ redundancy version is used (required        for de-rate-matching) and/or which modulation constellation        version is used (required for demodulation).    -   UE Identity (UE ID): Tells for which user equipment the L1/L2        control signaling is intended for. In typical implementations        this information is used to mask the CRC of the L1/L2 control        signaling in order to prevent other user equipments to read this        information.

To enable an uplink packet data transmission, L1/L2 control signaling istransmitted on the downlink (PDCCH) to tell the user equipment about thetransmission details. This L1/L2 control signaling typically containsinformation on:

-   -   The physical resource(s) on which the user equipment should        transmit the data (e.g., subcarriers or subcarrier blocks in        case of OFDM, codes in case of CDMA).    -   When user equipment is configured to have a Carrier Indication        Field (CIF) in the L1/L2 control signaling, this information        identifies the component carrier for which the specific control        signaling information is intended. This enables assignments to        be sent on one component carrier which are intended for another        component carrier. This other, cross-scheduled component carrier        may be for example a PDCCH-less component carrier, i.e., the        cross-scheduled component carrier does not carry any L1/L2        control signaling.    -   L1/L2 control signaling for uplink grants is sent on the DL        component carrier that is linked with the uplink component        carrier or on one of the several DL component carriers, if        several DL component carriers link to the same UL component        carrier.    -   The Transport Format, the user equipment should use for the        transmission. This can be the transport block size of the data        (payload size, information bits size), the MCS (Modulation and        Coding Scheme) level, the Spectral Efficiency, the code rate,        etc. This information (usually together with the resource        allocation (e.g., the number of resource blocks assigned to the        user equipment)) allows the user equipment (transmitter) to pick        the information bit size, the modulation scheme and the code        rate in order to start the modulation, the rate-matching and the        encoding process. In some cases the modulation scheme maybe        signaled explicitly.    -   Hybrid ARQ information:    -   HARQ Process number: Tells the user equipment from which hybrid        ARQ process it should pick the data.    -   Sequence number or new data indicator: Tells the user equipment        to transmit a new packet or to retransmit a packet. If soft        combining is implemented in the HARQ protocol, the sequence        number or new data indicator together with the HARQ process        number enables soft-combining of the transmissions for a        protocol data unit (PDU) prior to decoding.    -   Redundancy and/or constellation version: Tells the user        equipment, which hybrid ARQ redundancy version to use (required        for rate-matching) and/or which modulation constellation version        to use (required for modulation).    -   UE Identity (UE ID): Tells which user equipment should transmit        data. In typical implementations this information is used to        mask the CRC of the L1/L2 control signaling in order to prevent        other user equipments to read this information.

There are several different possibilities how to exactly transmit theinformation pieces mentioned above in uplink and downlink datatransmission. Moreover, in uplink and downlink, the L1/L2 controlinformation may also contain additional information or may omit some ofthe information. For example:

-   -   HARQ process number may not be needed, i.e., is not signaled, in        case of a synchronous HARQ protocol.    -   A redundancy and/or constellation version may not be needed, and        thus not signaled, if Chase Combining is used (always the same        redundancy and/or constellation version) or if the sequence of        redundancy and/or constellation versions is pre-defined.    -   Power control information may be additionally included in the        control signaling.    -   MIMO related control information, such as e.g., pre-coding, may        be additionally included in the control signaling.    -   In case of multi-codeword MIMO transmission transport format        and/or HARQ information for multiple codewords may be included.

For uplink resource assignments (on the Physical Uplink Shared Channel(PUSCH)) signaled on PDCCH in LTE, the L1/L2 control information doesnot contain a HARQ process number, since a synchronous HARQ protocol isemployed for LTE uplink. The HARQ process to be used for an uplinktransmission is given by the timing. Furthermore, it should be notedthat the redundancy version (RV) information is jointly encoded with thetransport format information, i.e., the RV info is embedded in thetransport format (TF) field. The Transport Format (TF) respectivelymodulation and coding scheme (MCS) field has for example a size of 5bits, which corresponds to 32 entries. 3 TF/MCS table entries arereserved for indicating redundancy versions (RVs) 1, 2 or 3. Theremaining MCS table entries are used to signal the MCS level (TBS)implicitly indicating RV0. The size of the CRC field of the PDCCH is 16bits.

For downlink assignments (PDSCH) signaled on PDCCH in LTE the RedundancyVersion (RV) is signaled separately in a two-bit field. Furthermore themodulation order information is jointly encoded with the transportformat information. Similar to the uplink case there is 5 bit MCS fieldsignaled on PDCCH. 3 of the entries are reserved to signal an explicitmodulation order, providing no Transport format (Transport block) info.For the remaining 29 entries modulation order and Transport block sizeinfo are signaled.

Physical Downlink Control Channel (PDCCH)

As already explained, a PDCCH carriers messages as DCIs. Each PDCCH istransmitted on an aggregation of one or more so called Control ChannelElements (CCEs), where each CCE corresponds to nine Resource ElementGroups (REGs, i.e., sets of four physical resource elements). REGsconstituting CCEs are not consecutive and CCEs are distributed infrequency over entire bandwidth. Note that CCEs are spread in frequencydomain to achieve frequency diversity. Four PDCCH formats are supportedas listed in the following table, which also shows the correspondingpossible CCE aggregation levels.

PDDCH Number of Number Number of format CCEs of REGs PDCCH bits 0 1 9 721 2 18 144 2 4 36 288 3 8 72 576

CCEs are numbered and used consecutively, and to simplify the decodingprocess, a PDCCH with a format consisting of n CCEs may only start witha CCE with a number equal to a multiple of n.

The number of available CCEs in a cell varies; it may be semi static(System bandwidth, PHICH configuration) or dynamic (PCFICH).

The number of CCEs used for transmission of a particular PDCCH isdetermined by the eNodeB according to channel conditions. For example,if the PDCCH is intended for a mobile terminal with a good downlinkchannel, (e.g., close to the eNodeB) then one CCE is likely to besufficient. However, for a mobile terminal with a poor channel (e.g.,near the cell border) then eight CCEs may be required in order toachieve sufficient robustness. In addition, the power level of a PDCCHmay be adjusted to match the channel conditions.

In detecting a PDCCH, the mobile terminal shall monitor a set of PDCCHcandidates for control information in every non-DRX subframe, wheremonitoring refers to the process of attempting to decode each of PDCCHsin the set according to all DCI formats, as will be explained in moredetail later.

In order that the mobile terminal can identify whether it has received aPDDCH transmission correctly, error detection is provided by means of a16-bit CRC appended to each PDCCH. Furthermore, it is necessary that theUE can identify which PDCCHs are intended for it. This could in theorybe achieved by adding an identifier to the PDCCH payload; however, itturns out to be more efficient to scramble the CRC with the UE identity(e.g., C-RNTI, Cell Radio Network Temporary Identifier), which saves theadditional payload but at the cost of a small increase in theprobability of falsely detecting a PDCCH intended for another UE.

The Physical Control Format Indicator Channel (PCFICH) carries a ControlFormat Indicator (CFI) which indicates the number of OFDM symbols usedfor transmission of control channel information in each subframe. TheeNodeB is capable of transmitting multiple PDCCHs in a subframe. Thetransmissions are organized such that a UE can locate the PDCCHsintended for it, while at the same time making efficient use of theresources allocated for PDCCH transmissions.

A simple approach, at least for the eNodeB, would be to allow the eNodeBto place any PDCCH anywhere in the PDCCH resources (or CCEs) indicatedby the PCFICH. In this case, the UE would need to check all possiblePDCCH locations, PDCCH formats and DCI formats, and act on thosemessages with correct CRCs (taking into account the CRC is scrambledwith a UE identity). Carrying out such a blind decoding of all thepossible combinations would require the UE to make many PDDCH decodingattempts in every subframe. For small system bandwidths thecomputational load might be reasonable, but for large system bandwidthswith a large number of possible PDCCH locations, it would become asignificant burden, leading to excessive power consumption in the UEreceiver.

The alternative approach adopted for LTE is to define for each UE alimited set of CCE locations where a PDCCH may be placed. Such aconstraint may lead to some limitations as to which UEs can be sentPDCCHs within the same subframe, which would thus restrict the UEs towhich the eNodeB could grant resources. Therefore, it is important forgood system performance that the set of possible PDCCHs locationsavailable for each UE is not too small. The set of CCE locations inwhich the UE may find its PDCCHs can be considered as a search space. InLTE the search space is of different size for each PDCCH format.Moreover, separate dedicated and common search spaces are defined, wherea dedicated search space is configured for each UE individually, whileall UEs are informed of the extent of the common search space. Note thatthe dedicated and common search spaces may overlap for a given UE.

With small search spaces it is quite possible in a given subframe thatthe eNodeB cannot find CCE resources to send PDCCHs to all the UEs thatit would like to, because, having assigned some CCE locations, theremaining CCE locations are not in the search space of a particular UE.

In order to keep under control the computational load arising from thetotal number of blind decoding attempts, the UE is not required tosearch for all the defined DCI formats simultaneously.

In the common search space the UE will search for DCI Formats 1A and 1C.In addition, the UE may be configured to search for Format 3 or 3A,which have the same size as DCI formats 0 and 1A, and may bedistinguished by having the CRC scrambled by different (common) identity(e.g., PC-PUCCH-RNTI), rather than a UE-specific one (e.g., C-RNTI). Inparticular, PC-PUCCH-RNTI (Transmit Power Control-Physical UplinkControl Channel-RNTI) and TPC-PUSCH-RNTI (Transmit PowerControl-Physical Uplink Shared Channel-RNTI) are used in said respect.

DCI formats 0, 1A, 1C, 3 and 3A have two different payload sizes. Thecommon search space is monitored by all UEs and may correspond to CCEs0-15, rendering 4 decoding candidates with PDCCH format 2: 0-3, 4-7,8-11, 12-15, or 2 decoding candidates with PDCCH format 3: 0-7, 8-15. Inthis case, there would be six blind decode attempts per payload size,and two different PDCCH payload sizes, thus having a total number ofblind decodes per UE of 12.

The power-control message of DCI Format 3, 3A is directed to a group ofterminals using an RNTI specific for that group. Each terminal can beallocated two power-control RNTIs, one for PUCCH power control and theother for PUSCH power control.

Typically, in the dedicated search space, the UE will always search forDCI formats 0 and 1A, which are both the same size and are distinguishedby a flag in the message. In addition, a UE may be required to receivefurther DCI formats (e.g., 1, 1B or 2) depending on the PDSCHtransmission mode configured by the eNodeB.

The starting location of the UE specific search space is usuallydetermined by a hashing function based, e.g., on the slot number withinthe radio frame, the RNTI value and other parameters. The UE specificsearch space allows aggregation levels of 1, 2, 4 and 8 CCEs.

Further information is provided in LTE—The UMTS Long Term Evolution—FromTheory to Practice, Edited by Stefanie Sesia, Issam Toufik, MatthewBaker, Chapter 9.3, incorporated herein by reference.

DRX (Discontinuous Reception)

DRX functionality can be configured for RRC_IDLE, in which case the UEuses either the specific or default DRX value (defaultPagingCycle); thedefault is broadcasted in the System Information, and can have values of32, 64, 128 and 256 radio frames. If both specific and default valuesare available, the shorter value of the two is chosen by the UE. The UEneeds to wake up for one paging occasion per DRX cycle, the pagingoccasion being one subframe.

DRX functionality can be also configured for an “RRC_CONNECTED” UE, sothat it does not always need to monitor the downlink channels. In orderto provide reasonable battery consumption of user equipment, 3GPP LTE(Release 8/9) as well as 3GPP LTE-A (Release 10) provides a concept ofdiscontinuous reception (DRX). Technical Standard TS 36.321 Chapter 5.7explains the DRX and is incorporated by reference herein.

The following parameters are available to define the DRX UE behavior;i.e., the On-Duration periods at which the mobile node is active, andthe periods where the mobile node is in a DRX mode.

-   -   On duration: duration in downlink subframes that the user        equipment, after waking up from DRX, receives and monitors the        PDCCH. If the user equipment successfully decodes a PDCCH, the        user equipment stays awake and starts the inactivity timer;        [1-200 subframes; 16 steps: 1-6, 10-60, 80, 100, 200]    -   DRX inactivity timer: duration in downlink subframes that the        user equipment waits to successfully decode a PDCCH, from the        last successful decoding of a PDCCH; when the UE fails to decode        a PDCCH during this period, it re-enters DRX. The user equipment        shall restart the inactivity timer following a single successful        decoding of a PDCCH for a first transmission only (i.e., not for        retransmissions). [1-2560 subframes; 22 steps, 10 spares: 1-6,        8, 10-60, 80, 100-300, 500, 750, 1280, 1920, 2560]    -   DRX Retransmission timer: specifies the number of consecutive        PDCCH subframes where a downlink retransmission is expected by        the UE after the first available retransmission time. [1-33        subframes, 8 steps: 1, 2, 4, 6, 8, 16, 24, 33]    -   DRX short cycle: specifies the periodic repetition of the on        duration followed by a possible period of inactivity for the        short DRX cycle. This parameter is optional. [2-640 subframes;        16 steps: 2, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256,        320, 512, 640]    -   DRX short cycle timer: specifies the number of consecutive        subframes the UE follows the short DRX cycle after the DRX        Inactivity Timer has expired. This parameter is optional. [1-16        subframes]    -   Long DRX Cycle Start offset: specifies the periodic repetition        of the on duration followed by a possible period of inactivity        for the DRX long cycle as well as an offset in subframes when        on-duration starts (determined by formula defined in TS 36.321        section 5.7); [cycle length 10-2560 subframes; 16 steps: 10, 20,        30, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280,        2048, 2560; offset is an integer between [0—subframe length of        chosen cycle]]

The total duration that the UE is awake is called “Active time”. TheActive Time includes the on-duration of the DRX cycle, the time UE isperforming continuous reception while the inactivity timer has notexpired and the time UE is performing continuous reception while waitingfor a downlink retransmission after one HRQ RTT. Based on the above, theminimum active time is of length equal to on-duration, and the maximumis undefined (infinite).

The operation of DRX gives the mobile terminal the opportunity todeactivate the radio circuits repeatedly (according to the currentlyactive DRX cycle) in order to save power. Whether the UE indeed remainsin DRX (i.e., is not active) during the DRX period may be decided by theUE; for example, the UE usually performs inter-frequency measurementswhich cannot be conducted during the On-Duration, and thus need to beperformed some other time, during the DRX opportunity of time.

The parameterization of the DRX cycle involves a trade-off betweenbattery saving and latency. For example, in case of a web browsingservice, it is usually a waste of resources for a UE to continuouslyreceive downlink channels while the user is reading a downloaded webpage. On the one hand, a long DRX period is beneficial for lengtheningthe UE's battery life. On the other hand, a short DRX period is betterfor faster response when data transfer is resumed—for example when auser requests another web page.

To meet these conflicting requirements, two DRX cycles—a short cycle anda long cycle—can be configured for each UE; the short DRX cycle isoptional, i.e., only the long DRX cycle is used. The transition betweenthe short DRX cycle, the long DRX cycle and continuous reception iscontrolled either by a timer or by explicit commands from the eNodeB. Insome sense, the short DRX cycle can be considered as a confirmationperiod in case a late packet arrives, before the UE enters the long DRXcycle. If data arrives at the eNodeB while the UE is in the short DRXcycle, the data is scheduled for transmission at the next on-durationtime, and the UE then resumes continuous reception. On the other hand,if no data arrives at the eNodeB during the short DRX cycle, the UEenters the long DRX cycle, assuming that the packet activity is finishedfor the time being.

During the Active Time the UE monitors PDCCH, reports SRS (SoundingReference Signal) as configured and reports CQI (Channel QualityInformation)/PMI (Precoding Matrix Indicator)/RI (Rank Indicator)/PTI(Precoder Type Indication) on PUCCH. When UE is not in Active time,type-0-triggered SRS and CQI/PMI/RI/PTI on PUCCH may not be reported. IfCQI masking is set up for the UE, the reporting of CQI/PMI/RI/PTI onPUCCH is limited to On Duration.

Available DRX values are controlled by the network and start fromnon-DRX up to x seconds. Value x may be as long as the paging DRX usedin RRC_IDLE. Measurement requirements and reporting criteria can differaccording to the length of the DRX interval, i.e., long DRX intervalsmay have more relaxed requirements (for more details see further below).

FIG. 8 discloses an example of DRX. The UE checks for schedulingmessages (indicated by its C-RNTI, cell radio network temporaryidentity, on the PDCCH) during the “on duration” period, which is thesame for the long DRX cycle and the short DRX cycle. When a schedulingmessage is received during an “on duration”, the UE starts an“inactivity timer” and monitors the PDCCH in every subframe while theInactivity Timer is running. During this period, the UE can be regardedas being in a continuous reception mode. Whenever a scheduling messageis received while the Inactivity Timer is running, the UE restarts theInactivity Timer, and when it expires the UE moves into a short DRXcycle and starts a “short DRX cycle timer”. The short DRX cycle may alsobe initiated by means of a MAC Control Element. When the short DRX cycletimer expires, the UE moves into a long DRX cycle.

In addition to this DRX behavior, a ‘HARQ Round Trip Time (RTT) timer’is defined with the aim of allowing the UE to sleep during the HARQ RTT.When decoding of a downlink transport block for one HARQ process fails,the UE can assume that the next retransmission of the transport blockwill occur after at least ‘HARQ RTT’ subframes. While the HARQ RTT timeris running, the UE does not need to monitor the PDCCH. At the expiry ofthe HARQ RTT timer, the UE resumes reception of the PDCCH as normal.

There is only one DRX cycle per user equipment. All aggregated componentcarriers follow this DRX pattern.

FIG. 9 illustrates the DRX operation of a UE having a long DRX cyclewith a high number of subframes, whereas FIG. 10 illustrates the DRXoperation of a UE having a long DRX cycle with a low number ofsubframes. As can be seen from these figures, the “short” long DRX cycleof FIG. 10 is advantageous in that the eNodeB does not have to wait toolong for an opportunity to schedule the UE, compared to the long DRXcycle of FIG. 9.

Fast Dormancy

Smart phones have an increasing number of applications that only send asmall amount of data, but the transmission frequency of the packets isrelatively high. Such always-on applications include for example, email,instant messaging and widgets. It is important to keep UE powerconsumption low while having frequent transmissions. The UE could bemoved to idle state for low power consumption. However, the idle stateshould be avoided because the next packet will then cause packetconnection set-up, leading to increased latencies and signaling trafficin the network.

In order to keep UE power consumption low, the proprietary (i.e.,functionality not defined by 3GPP standards) fast dormancy wasintroduced. When using fast dormancy, the mobile application informs theradio layers when the data transmission is over, and the UE can thensend the Signaling Connection Release Indication (SCRI) to the RNCsimulating a failure in the signaling connection. Consequently, the UEreleases the RRC connection and moves to idle state. This approach keepsthe UE power consumption low, but it causes frequent set-ups of packetconnections unnecessarily increasing the signaling load. In addition,the network counters indicate a large number of signaling connectionfailures as this battery-saving method cannot be distinguished from agenuine signaling connection failure in the network.

3GPP Release 8 specified Fast Dormancy functionality, clarifying the UEbehavior and providing the network with information of what the UEactually wants to do, but leaving the network in charge of the UE RRCstate. Put differently, the UE is not allowed to release the RRCconnection and move to idle on its own without network control. Forfurther information on Fast Dormancy: WCDMA For UMTS—HSPA Evolution andLTE—Fifth Edition; Edited by Harri Holma and Antti Toskala, Chapter15.6.

Measurements

Measurements performed by an UE are part of the Radio ResourceManagement and configured by the eNB. They mainly (but not exclusively)serve the purpose of handling mobility with other LTE cells or cellsbelonging to other Radio Access Technologies (RATs).

The Radio Resource Management procedures (specified in TS 36.133)distinguish between measurements performed in RRC_IDLE state andRRC_CONNECTED state. In the following intra-frequency measurements(i.e., the measurements on the serving cell(s) and cells located in thesame frequency band), inter-frequency measurements (i.e., themeasurements for cells on a frequency band different from that of thecurrent serving cell(s)) and inter-RAT (i.e., measurements for thosecells operating with other radio access technologies than UTRAN) aredescribed in more detail with a focus on the RRC_CONNECTED state and themeasurement requirements that UE has to follow when it is indiscontinuous reception (DRX).

Intra-Frequency Measurements

LTE intra frequency monitoring aims at performing measurements both onthe serving cell and on neighboring cells which use the same carrierfrequency as the serving cell.

When DRX activity is enabled, the UE must be able to take advantage ofthe opportunities to save power between subsequent DRX on periods“.Intra-frequency monitoring performance relaxations will only be definedfor those cases where the periodicity of the on period” is larger than40 ms (Chapter 13.6.1.1 of LTE—The UMTS Long Term Evolution, Edited by:Stefania Sesia, Issam Toufik, Matthew Baker, 2009).

For measurements in the RRC_CONNECTED state when DRX is in use, theamount of intra-frequency measurements (as well as the inter-frequencyand inter-RAT, see below) that are to be performed, depend on the DRXcycle length of the long DRX cycle. The below table discloses the timesT_Identify and T_Measure in seconds depending on the amount of subframesof the DRX cycle.

In order to be able to perform RSRP (Reference Signal Receive Power) andRSRQ (Reference Signal Reference Quality) measurements, the UE mustfirst synchronize to and determine the cell ID of neighbor cells;T_identify is the time the UE is required to perform the identificationof neighboring cells it is not aware of yet; e.g., when the DRX cycle isbetween 40 and 80 subframes long, the UE needs to have finished theidentification of neighboring cells within 40 DRX cycles (i.e., 1.6 to3.2 seconds). T_Measure defines how long the UE has time to perform theintra-frequency measurements on the serving and neighboring cells; e.g.,when the DRX cycle is 128 subframes, the UE needs to have finished theintra-frequency measurements within 5 DRX cycles (i.e., 0.64 seconds).

The exact timing when the cell identification and the measurements areperformed, depends on the UE implementation. For example, theintra-frequency measurements which do not necessitate recalibrating theradio to another frequency (in contrast to inter-frequencymeasurements), the cell identification and measurements could beperformed during the On-Duration where the UE is already active.

It is assumed that five measurement samples are necessary to obtain anaccurate measurement results, and one subframe for every measurementsample is sufficient. See TS 36.133 Table 8.1.2.2.1.2-2 where T_Measureis indicated to be 0.2 seconds for a DRX cycle of less than 40subframes, and 5 cycles for DRX cycles of >=40 subframes. This concludesthat with a DRX cycle length of, e.g., 40 subframes, the measurementwill be obtained within 200 ms. The cell identification may be operatedin parallel to the intra-frequency measurements.

However, cell identification might require a longer time span withineach DRX cycle, e.g., 5 ms.

DRX cycle (subframes) <40 40-80 128 >128 T Identify(s) 0.8 1.6-3.2 3.23.2-51.2 (40 cycles) (25 cycles) (20 cycles) T Measure(s) 0.2 0.2-0.40.64 0.8-12.8 (5 cycles) (5 cycles) (5 cycles)

Inter-Frequency Measurements

LTE inter-frequency monitoring is very similar to intra-frequencymonitoring. When the UE is not in DRX), the inter-frequency measurementis implemented using monitoring gaps. For a 6 ms gap pattern only 5 msare available for inter-frequency monitoring, once the switching timehas been removed; i.e., the time for the radio frequency tuning is 1 ms.UE may have 8 times (80 ms gap period) or 16 times (40 ms gap period)for measurement in 640 ms. The 5 ms stems from primary and secondarysynch-channels existing every 5 ms for cell identification.

If the monitoring gaps repeat every 40 ms only 5/40=12.5% is availablefor inter-frequency monitoring. For this reason LTE inter-frequencymaximum cell identification time and measurement periods need to belonger than for the intra-frequency case.

Within one monitoring gap the presence of the PSS (PrimarySynchronization Symbol) and SSS (Secondary Synchronization Symbol)symbols is guaranteed since they repeat every 5 ms, and there is alsosufficient reference signals (RS) to perform power accumulation andobtain a measurement sample for RSRP calculation. There is alsosufficient signal to perform an LTE carrier RSSI (Received SignalStrength Indicator) measurement to derive RSRQ.

Similar to the intra-frequency case, if the UE is in DRX mode, someperformance relaxation is required to ensure that the UE can takeadvantage of the DRX periods to save power. How long the UE takes onlyfor measurement but not for identification is UE implementationdependent. The UE will use more than 5 ms for both measurement andidentification. This time period for cell identification and measurementis outside the Active Time, in order to be able to retune the radiofrequency part of the receiver to the other frequency.

The below table is exemplary for a gap pattern ID 0 and Nfreq=1, anddiscloses the time requirements for the identification of neighboringcells and the inter-frequency measurements depending on the amount ofsubframes of the currently active DRX cycle.

DRX cycle (subframes) <=160 256 320 >320 T Identify(s) 3.84 5.12 6.410.24-51.2 (20 cycles) (20 cycles) (20 cycles) T Measure(s) 0.48 1.281.6  1.6-12.8 (5 cycles) (5 cycles) (5 cycles)

Inter RAT (Radio Access Technology)

Inter-RAT measurements refer to downlink physical channels belonging toanother radio access technology than UTRAN, e.g., GSM. The below tableis an example for gap pattern ID 0, Nfreq=1 and UTRA_FDD.

DRX cycle (subframes) <=40 64 80 128 160 >160 Identify (s) 2.4 2.56 (403.2 (40 3.2 (25 3.2 (20 10.24-51.2 cycles) cycles) cycles) cycles) (20cyc.) Measure (s) 0.48 0.48 0.48 0.64 0.8 (5 1.28-12.8 cycles) (5cycles)Disadvantages of the Prior Art

As already explained above, the short and long DRX cycles allow atrade-off between a high battery saving and a fast response to datascheduling.

This waste of battery power is further exacerbated by the measurementand reporting requirements imposed on the UE and which depend on thelong DRX cycle. As explained above, intra-frequency, inter-frequency andinter-RAT measurements are to be performed by the mobile terminal withintime intervals depending on the actual DRX cycle length. Furthermore, inthe active time the UE has to report SRS and CQI/PMI/RI/PTI on thePUCCH.

The intra-frequency measurements can be performed during the On-durationof the DRX operation, provided the On-duration is sufficiently long toperform said measurements, i.e., at least 5 subframes. On the otherhand, inter-frequency measurements need to be performed during one ofthe DRX opportunities where the UE is allowed to be inactive, since theradio tuner needs to be calibrated to another frequency, which maytypically take 6 subframes.

Since the measurements requirements depend on the long DRX cyclesubframe length, a short DRX cycle results in that the UE has to performthe measurements more times. Taking intra-frequency measurements as anexample, for a long DRX cycle length of 40 subframes, the UE has torepeatedly identify neighboring cells within 1.6 s, and has to performintra-frequency measurements within 0.2 s. The time requirements arerelaxed for a long DRX cycle length of, e.g., 2560 subframes, where theneighboring cell identification has to be performed within 51.2 s andthe intra-frequency measurements within 12.8 s (see table above).

Thus, in case the long DRX cycle is shortened to allow a reducedresponse time for data transmission/reception, the impact on the batterydue to the On-duration and also the measurement requirements is high.

Therefore, it is important to allow a fast response time of the UE withonly a minimum impact on the battery consumption of the UE.

BRIEF SUMMARY

The present disclosure strives to avoid the various disadvantagesmentioned above.

One object of the disclosure is to propose a mechanism for an improveddiscontinuous reception operation at the mobile terminal.

The object is solved by the subject matter of the independent claims.Advantageous embodiments are subject to the dependent claims.

According to a first aspect, the disclosure suggests an improvement tothe DRX operation of the prior art by introducing an additional DRXcycle, a so called DRX wake-up cycle, which runs in parallel to theshort and/or long DRX cycle already standardized and known from theprior art. The operation of the mobile terminal with regard to the shortand long DRX cycle needs not be changed to implement the presentdisclosure. The mobile terminal performs the DRX wake-up cycle operationas follows.

The wake-up cycle defines time intervals after which the mobile terminalstarts monitoring the downlink control channel for a particular timeduration, in the following called wake-up duration. The time intervalsof the wake-up cycle between the wake-up durations are preferablyshorter than the one of the DRX long cycle, and may have the same or ashorter length than the ones of the DRX short cycle. The wake-upduration may be as long as the on-duration of the DRX short/long cycle,or may be preferably much shorter, such as only one or a few subframes.

Furthermore, in one embodiment of the disclosure the mobile terminalmonitors the downlink control channel in a same way as during theon-duration of the short/long DRX cycle; i.e., the mobile terminalmonitors for the same downlink control channel messages destined toitself during the wake-up duration as during the on-duration. Preferablyhowever, the mobile terminal does not monitor the downlink controlchannel for all possible messages, but only for particular messages,e.g., such as for downlink and uplink scheduling messages.

The wake-up duration according to the DRX wake-up cycle furtherdifferentiates from the on-duration according to the DRX short/longcycle, in that the mobile terminal operates only to monitor the downlinkcontrol channel during the wake-up duration, whereas the mobile terminalhas to perform further functions during the on-duration besides themonitoring of the downlink control channel, such as measurements andreporting as explained in the background section.

Furthermore, the mobile terminal operation according to the DRX wake-upcycle may start at the same time as the one according to the DRX shortor long cycle. In more detail, in one embodiment of the disclosure theinactivity timer of the mobile terminal expires and the mobile terminalmay thus enter the DRX mode, starting, e.g., the DRX short cycle asexplained in the background section. At the same time however, themobile terminal may also start the operation according to the DRXwake-up cycle. Alternatively, the mobile may start the operationaccording to the DRX wake-up cycle in parallel with the DRX long cycle,i.e., after expiry of the DRX short cycle timer; in this case, the DRXwake-up cycle runs in parallel to only the DRX long cycle, but not inparallel to the DRX short cycle. As a further alternative, the mobileterminal may start the operation according to the DRX wake-up cycle whenthe mobile terminal starts the DRX short cycle but stops the DRX wake-upcycle when the mobile terminal enters the DRX long cycle.

A further important aspect to the disclosure is that the measurement andreporting requirements (e.g., intra-frequency, inter-frequency,inter-RAT, CQI reporting) are still depending on the length of theintervals of the DRX long cycle; the measurement and reportingrequirements are not influenced by the DRX wake-up cycle introduced bythe embodiments of the disclosure. Correspondingly, while the mobileterminal has the opportunity of waking-up more often, it does not needto perform measurements or reporting more often.

As with the mobile terminal operation of the DRX short/long cycle, themobile terminal becomes active when during the wake-up duration of theDRX wake-up cycle it detects a downlink control channel message destinedto itself. For instance, the base station, controlling the cell to whichthe mobile terminal is attached, sends a scheduling message to themobile terminal in case the mobile terminal is to transmit and/orreceive data in the uplink and/or the downlink. The base station,knowing the DRX wake-up cycle and the corresponding wake-upopportunities given by the wake-up duration, transmits the schedulingmessage in the particular subframe or one of the particular subframes ofthe wake-up duration. The mobile terminal for the wake-up durationchecks the downlink control channel for such messages, and thus detectsthe scheduling message transmitted by the base station. The mobileterminal may thus decode the scheduling message and becomes active so asto perform the necessary operation for receiving respectivelytransmitting the data according to the scheduling message.

The present disclosure thus combines the advantages of the DRX short andlong cycle while avoiding the disadvantages thereof. In more detail,since the DRX wake-up cycle preferably implements short intervalsbetween the wake-up opportunities of the wake-up duration, the responsetime of the mobile terminal may be greatly reduced, thus allowing thebase station to schedule the mobile terminal sooner. At the same time,since the wake-up duration preferably spans only one or a few subframes,the impact on the battery saving is minimal and the battery consumptionis only slightly increased, especially, compared to having a very shortlong DRX cycle or short DRX cycle. This is even more so, since themeasurement and reporting requirements imposed on the mobile terminalstill only depend on the long DRX cycle, where intervals are usuallymuch longer than those of the DRX wake-up cycle.

The present disclosure provides a method for discontinuous reception fora mobile terminal being in communication with a base station in a mobilecommunication system. The mobile terminal is configured by the basestation with a first discontinuous reception cycle and an additionaldiscontinuous reception cycle. After time intervals according to thefirst discontinuous reception cycle, the mobile terminal becomes activefor an on-duration of time. In parallel to becoming active according tothe first discontinuous reception cycle and after time intervalsaccording to the additional discontinuous reception cycle, the mobileterminal monitors the downlink control channel for messages destined tothe mobile terminal for a particular duration of time.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminalstarts the discontinuous reception according to the first discontinuousreception cycle and the additional discontinuous reception cycle at thesame time or with a predetermined time offset between each other.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminalduring the particular duration of time is not active and preferably onlyperforms the monitoring of the downlink control channel for messagesdestined to the mobile terminal.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the particular durationof time is at least one subframe. In a preferred embodiment, the timeintervals according to the first discontinuous reception cycle arelonger than the time intervals according to the additional discontinuousreception cycle.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminal indiscontinuous reception mode is to perform measurements. Measurementrequirements for the measurements depend on the first discontinuousreception cycle. In a preferred embodiment, the measurement requirementscomprise measurement requirements for intra-frequency measurementsaccording to which the mobile terminal is to identify neighboring cellswithin a first time period and is to perform the intra-frequencymeasurements within a second time period. In another preferredembodiment, the measurement requirements comprise measurementrequirements for inter-frequency measurements according to which themobile terminal is to identify neighboring cells within a third timeperiod and is to perform the inter-frequency measurements within afourth time period. In still another preferred embodiment, themeasurement requirements comprise measurement requirements for interradio access technology measurements according to which the mobileterminal is to identify neighboring cells within a fifth time period andis to perform the inter-radio access technology measurements within asixth time period.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminalduring the on-duration of time transmits to the base station soundingreference signals and/or transmits results of measurements previouslyperformed by the mobile terminal. In a preferred embodiment, themeasurement results to be transmitted to the base station comprise atleast one of the following: channel quality information, precodingmatrix indicator, rank indicator, precoder type indication.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the first discontinuousreception cycle is a long discontinuous reception cycle, wherein themobile terminal is further configured with a short discontinuousreception cycle. After time intervals according to the shortdiscontinuous reception cycle, the mobile terminal becomes active forthe on-duration of time. The time intervals according to the shortdiscontinuous reception cycle are different from the time intervalsaccording to the long discontinuous reception cycle. The mobile terminaloperates according to the short discontinuous reception cycle until ashort discontinuous reception cycle timer expires, and upon expiry ofthe short discontinuous reception cycle timer, the mobile terminaloperates in parallel according to the long discontinuous reception cycleand according to the additional discontinuous reception cycle.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the messages for whichthe mobile terminal monitors the downlink control channel for theparticular duration of time refer only to scheduling. In addition oralternatively, the mobile terminal monitors the downlink control channelfor the particular duration of time only for messages according to atleast but not all of predetermined downlink control information formats.In addition or alternatively the mobile terminal monitors the downlinkcontrol channel for the particular duration of time only for messagesthat request the mobile terminal to transmit a channel state informationreport.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminalmonitors the downlink control channel for the particular duration oftime only according to at least one but not all of predetermined formatsof the downlink control channel. In addition or alternatively, themobile terminal monitors the downlink control channel for the particularduration of time only in a predetermined limited search space.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminal isconfigured with one primary cell and at least one activated secondarycell. Wherein the mobile terminal monitors during the particularduration of time only the downlink control channel transmitted on theprimary cell. In a preferred embodiment the secondary cell is on adifferent frequency band than the primary cell.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, cross scheduling is usedfor the mobile terminal, performing scheduling on the at least onesecondary cell via scheduling messages transmitted over the primarycell. In this case, the mobile terminal may ignore scheduling messagesfor the secondary cell when monitoring the downlink control channel ofthe primary cell.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, measurement requirementsfor a secondary cell do not depend on the first discontinuous receptioncycle but depend on a measurement requirement cycle for a deactivatedsecondary cell.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminalmonitors the downlink control channel for the particular duration oftime only a predetermined number of times after the on-duration of thefirst discontinuous reception cycle. This is achieved in a preferredembodiment by using an enable timer that is started upon expiry of theactive time of the mobile terminal for the on-duration of time. Themobile terminal operates according to the additional discontinuous cycleonly when the enable timer is running.

In addition or alternatively, the mobile terminal monitors the downlinkcontrol channel for the particular duration of time only a predeterminednumber of times before the on-duration of the first discontinuousreception cycle. This is achieved in a preferred embodiment by using aprohibition timer that is started upon expiry of the active time of themobile terminal for the on-duration of time. The mobile terminaloperates according to the additional discontinuous cycle only when theprohibition timer is not running.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminalmonitors the downlink control channel only within a limited band offrequencies, preferably 1.4 MHz around the center frequency of thedownlink control channel.

The present disclosure further provides a mobile terminal for performingdiscontinuous reception and being in communication with a base stationin a mobile communication system. The mobile terminal is configured bythe base station with a first discontinuous reception cycle and anadditional discontinuous reception cycle. After time intervals accordingto the first discontinuous reception cycle, the mobile terminal becomesactive for an on-duration of time. In parallel to becoming activeaccording to the first discontinuous reception cycle and after timeintervals according to the additional discontinuous reception cycle, areceiver of the mobile terminal monitors the downlink control channelfor messages destined to the mobile terminal for a particular durationof time.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, a processor of themobile terminal and the receiver start the discontinuous receptionaccording to the first discontinuous reception cycle and the additionaldiscontinuous reception cycle at the same time or with a predeterminedtime offset between each other.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminal isnot active during the particular duration of time. In a preferredembodiment, the processor and receiver only perform the monitoring ofthe downlink control channel for messages destined to the mobileterminal.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the particular durationof time which the receiver monitors the downlink control channel is atleast one subframe. In a preferred embodiment, the time intervalsaccording to the first discontinuous reception cycle are longer than thetime intervals according to the additional discontinuous receptioncycle.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the receiver of themobile terminal in discontinuous reception mode is to performmeasurements. A processor of the mobile terminal determines measurementrequirements for the measurements based on the first discontinuousreception cycle. In a preferred embodiment the processor determinesmeasurement requirements for intra-frequency measurements; this includesdetermining a first time period, within which the processor and thereceiver identify neighboring cells, and a second time period withinwhich the processor and the receiver perform the intra-frequencymeasurements.

In a preferred embodiment, the processor determines measurementrequirements for inter-frequency measurements. This includes determininga third time period, within which the processor and the receiveridentify neighboring cells, and a fourth time period within which theprocessor and the receiver perform the inter-frequency measurements.

In a preferred embodiment, the processor determines measurementrequirements for inter radio access technology measurements. Thisincludes determining a fifth time period, within which the processor andthe receiver identify neighboring cells, and a sixth time period withinwhich the processor and the receiver perform the inter radio accesstechnology measurements.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminalcomprises a transmitter for transmitting to the base station soundingreference signals and/or results of measurements a processor of themobile terminal and the receiver performed previously.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the receiver monitorsthe downlink control channel for the particular duration of time onlyfor messages referring to scheduling. In addition or alternatively, thereceiver monitors the downlink control channel for the particularduration of time only for messages according to at least but not all ofpredetermined downlink control information formats. In addition oralternatively, the receiver monitors the downlink control channel forthe particular duration of time only for messages that request themobile terminal to transmit a channel state information report.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the receiver monitorsthe downlink control channel for the particular duration of time onlyaccording to at least but not all of predetermined formats of thedownlink control channel. In addition or alternatively, the receivermonitors the downlink control channel for particular duration of timeonly in a predetermined limited search space.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, the mobile terminal isconfigured with one primary cell and at least one activated secondarycell. The receiver monitors during the particular duration of time onlythe downlink control channel transmitted on the primary cell.

According to an advantageous embodiment of the disclosure which can beused in addition or alternatively to the above, a processor of themobile terminal starts an enable timer upon expiry of the active time ofthe mobile terminal for the on-duration of time. The processordetermines whether the enable timer is running, and only in case it isdetermined that the enable timer is running, the receiver monitors thedownlink control channel for the particular duration of time. Inaddition or alternatively, a processor of the mobile terminal starts aprohibition timer upon expiry of the active time of the mobile terminalfor the on-duration of time. The processor determines whether theprohibition timer is running, and only in case it is determined that theprohibition timer is not running, the receiver monitors the downlinkcontrol channel for the particular duration of time.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following the disclosure is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary overview of the overall E-UTRAN architectureof 3GPP LTE,

FIG. 3 shows exemplary subframe boundaries on a downlink componentcarrier as defined for 3GPP LTE (Release 8/9),

FIG. 4 shows an exemplary downlink resource grid of a downlink slot asdefined for 3GPP LTE (Release 8/9),

FIGS. 5 & 6 show the 3GPP LTE-A (Release 10) Layer 2 structure withactivated carrier aggregation for the downlink and uplink, respectively,

FIG. 7 shows a state diagram for a mobile terminal and in particular thestates RRC_CONNECTED and RRC_IDLE and the functions to be performed bythe mobile terminal in these states,

FIG. 8 illustrates the DRX operation of a mobile terminal, and inparticular the DRX opportunity, on-duration, according to the short andlong DRX cycle,

FIGS. 9 & 10 illustrate the tradeoff between the battery savingopportunities given to the UE by the DRX operation and the response timeto scheduling by the base station,

FIG. 11 illustrates the DRX operation of a mobile terminal including theadditional DRX wake-up cycle according to one embodiment of thedisclosure,

FIG. 12 illustrates the parallel operation of the DRX wake-up cycle andthe DRX long cycle, and the corresponding response times in casedownlink data arrives at the base station for the mobile terminal,

FIG. 13 illustrates a DRX long cycle of 2560 subframes and a DRX wake-upcycle of 160 subframes and depicts the gain in response time that can beachieved by the parallel DRX wake-up cycle,

FIG. 14 illustrates the DRX operation in the PCell and SCell accordingto another embodiment of the disclosure, where the DRX wake-up cycle isonly operated on PCell but not on SCell,

FIG. 15 illustrates the DRX operation in the PCell and SCell and inparticular the wake-up time of the SCell when receiving a PDDCH on thePCell,

FIG. 16 illustrates the DRX operation according to another embodiment ofthe disclosure, including a wake-up duration enable timer,

FIG. 17 illustrates the DRX operation according to another embodiment ofthe disclosure, including a wake-up duration prohibition timer,

FIG. 18 illustrates the DRX operation according to another embodiment ofthe disclosure, where paging occasions of the mobile terminal are usedto get a paging with a particular wake-up RNTI for wake-upopportunities, and

FIG. 19 illustrates the DRX operation according to another embodiment ofthe disclosure, where the SPS assignments are used to monitor the PDSCHfor a transport block.

DETAILED DESCRIPTION

The following paragraphs will describe various embodiments of thedisclosure. For exemplary purposes only, most of the embodiments areoutlined in relation to a radio access scheme according to 3GPP LTE(Release 8/9) and LTE-A (Release 10/11) mobile communication systems,partly discussed in the Technical Background section above. It should benoted that the disclosure may be advantageously used for example in amobile communication system such as 3GPP LTE-A (Release 10/11)communication systems as described in the Technical Background sectionabove, but the disclosure is not limited to its use in this particularexemplary communication networks.

The term “active” and “becoming active” used in the claims and in thedescription refers to the operation of the mobile terminal in thediscontinuous reception mode, where the mobile terminal wakes up andbecomes active for an on-duration of time, so as to, e.g., perform andreport measurements and monitor the PDCCH. As such, the expression isequivalent to the one used in the standardization of LTE of the UE“entering Active Time”.

One aspect of the disclosure is to improve the DRX operation of themobile terminal with regard to the response time and battery consumptionopportunity provided for the mobile terminal. To said end, thedisclosure introduces an additional DRX cycle (in the following calledDRX wake-up cycle), which runs in parallel to the DRX short and/or longcycle.

FIG. 11 illustrates the DRX wake-up cycle, in parallel to the DRX longcycle, according to one embodiment of the disclosure, and will be usedexemplary to explain the concepts behind the disclosure. FIG. 11 is tobe regarded as only exemplary and thus shall restrict the scope ofprotection of the disclosure to this particular embodiment.

The disclosure allows maintaining the UE operation for the DRX shortcycle and DRX long cycle unchanged compared to the standard. The DRXwake-up cycle introduced by this disclosure runs in parallel to the DRXshort and/or long cycle.

As apparent from FIG. 11, the DRX wake-up cycle runs in parallel withonly the DRX long cycle, and not the DRX short cycle. Correspondingly,the operation of the mobile terminal according to the DRX wake-up cycleis thus started at basically the same time as the one for the DRX longcycle, namely upon expiry of the Short DRX cycle Timer. Alternatively,the DRX wake-up cycle may start with a predetermined time offsetcompared to the DRX long cycle (not shown).

According to another embodiment not depicted in FIG. 11, the DRX wake-upcycle may start at the same time as the one for the DRX short cycle,i.e., upon expiry of the Inactivity Timer or when receiving acorresponding MAC CE from the base station. In addition, a time offsetcan be implemented compared to the DRX short cycle, which the mobileterminal waits before starting operating according the DRX wake-up cycletoo. A corresponding offset parameter for starting the DRX wake-up cyclemay be called wake-upDRX-CycleStartOffset and can assume any particularnumber of subframes, e.g., between 0 and the actual cycle length of theDRX wake-up cycle.

According to a further embodiment not depicted in FIG. 11, the DRXwake-up cycle may start at the same time as the one for the DRX shortcycle, i.e., upon expiry of the Inactivity Timer or when receiving acorresponding MAC CE from the base station and end again after theexpiry of the Short DRX Cycle timer. In addition, as described above, atime offset can be implemented compared to the DRX short cycle, whichthe mobile terminal waits before starting operating according the DRXwake-up cycle too.

According to another embodiment not depicted in FIG. 11, the DRX wake-upcycle may start at the same time as the one for the DRX short cycle onlyupon reception of a corresponding MAC CE from the base station, i.e.,only when the mobile terminal entered DRX short cycle commanded fromeNodeB. The usage of the DRX wake-up cycle will end again after theexpiry of the Short DRX Cycle timer.

With reference to FIG. 11, the DRX wake-up cycle and the DRX long cyclesimultaneously start with the expiry of the Short DRX Cycle Timer. Aftera time interval defined for the DRX wake-up cycle, the mobile terminalstarts monitoring the control regions for one subframe for PDCCH-sdestined to itself, which means for PDCCHs masked with one of the RNTIsassigned to the mobile terminal. Correspondingly, the mobile terminalpowers the necessary radio parts and performs various blind decodingattempts to check whether any message (any DCI format) is present foritself in this one subframe within the monitored control region. Itshould be noted that the mobile terminal only performs the monitoring ofthe control region of the subframe for PDCCHs without performing anyother operation.

If the mobile terminal does not find any message, it continues in theDRX mode and waits during the time interval of the DRX wake-up cycleuntil it again starts monitoring for the PDCCH for the wake-up durationof one subframe. This is repeatedly performed by the mobile terminaluntil the mobile terminal enters into Active Time, because it detects aPDCCH message destined to itself during the on-duration of the DRXshort/long cycle or during the wake-up duration of the DRX wake-upcycle.

It should be also noted that the behavior of the mobile terminal when itreceives a PDCCH message during the wake-up duration of the DRX wake-upcycle is the same as its behavior when it receives a PDCCH messageduring the on-duration of the DRX short/long cycle. In both cases, themobile terminal becomes active, i.e., enters Active Time in the nextsubframe (when the previous subframe was a wake-up duration) or stays inActive time (if the previous subframe was a DRX on-duration), e.g.,according to the message received in the PDCCH.

As apparent from FIG. 11, the time intervals between the wake-upopportunities provided in the DRX wake-up cycle are much shorter thanthe time intervals between the on-durations of the DRX long cycle.Though this is not strictly necessary, the DRX wake-up cycle should beshorter than the DRX long cycle to provide the advantage of improvingthe response time compared to only operating according to the DRX longcycle.

In one embodiment of the disclosure, the DRX wake-up cycle interval(i.e., the interval between the wake-up durations) can be the same asthe one configured for the DRX short cycle. Correspondingly, in thiscase the DRX wake-up cycle would reuse the parameter shortDRX-cycledefined for the DRX short cycle. Alternatively, a separate parameter mayof course be defined for the DRX wake-up cycle, for example awake-upDRX-cycle parameter which can assume any particular number ofsubframes, e.g., between 2 and 640 subframes in 16 steps, as with theshortDRX-cycle.

Similarly, the wake-up duration of the DRX wake-up cycle might be aslong as the on-duration of the DRX short/long cycle, thus being alsoconfigured by the onDurationTimer parameter. Though a long wake-upduration allows the base station more flexibility in transmitting thePDCCH message to the mobile terminal, the battery consumption isincreased with every subframe for which the mobile terminal monitors thePDCCH, which has an impact on the battery due to the comparatively shortDRX wake-up cycle. Thus, alternatively and more advantageously, thewake-up duration of the DRX wake-up cycle should be much shorter (e.g.,one subframe) and could be configured by a separate parameter, e.g.,called wake-upDurationTimer, which can assume a low number of subframessuch as between 1 and 8 subframes in 8 steps.

The measurement and reporting requirements (e.g., intra-frequency,inter-frequency, inter-RAT, CQI reporting) are still depending on thelength of the intervals of the DRX long cycle as explained in detail inthe Background Section; the measurement and reporting requirements arenot depending or influenced by the DRX wake-up cycle of the disclosure.Correspondingly, while the mobile terminal has the opportunity ofwaking-up more often, it does not need to perform measurements orreporting so often. The mobile terminal performs the necessarymeasurements during the DRX opportunities given by the Long DRX cycledepending on UE implementation; e.g., intra-frequency measurementsduring the on-duration, for inter-frequency measurements in one of theDRX opportunities the mobile terminal powers up its RF part, retunes theRF part to the corresponding frequency and performs the inter-frequencymeasurements.

The behavior of the mobile terminal during the wake-up duration isdifferent from the one during the on-duration. While the mobile terminalduring the on-duration is considered to be active, i.e., be in activetime, the mobile terminal during the wake-up duration is not as suchactive; it merely powers up the necessary parts to monitor the downlinkcontrol region for PDCCHs addressed to its assigned RNTIs, thisprocedure including the blind decoding of the various DCI formats.During the wake-up duration, the mobile terminal does not have toperform any reporting of CSI or other measurements; it thus onlymonitors for the PDCCHs.

In case the wake-up duration according to the DRX wake-up cycle falls ona subframe which is also part of the on-duration according to one of theother DRX short/long cycle (as in FIG. 11), the UE behavior follows theone of the DRX short/long cycle. In other words, when the wake-upduration and the on-duration fall together (or overlap for somesubframes) the DRX wake-up duration is overwritten by the on-duration ofthe DRX short/long cycle. Basically, since the mobile terminal duringevery subframe of the on-duration monitors for PDCCHs (in the same wayas it does during the wake-up duration), the functioning of the DRXwake-up cycle is not affected by this coincidence of on-duration andwake-up duration.

FIG. 12 discloses one example of the different scheduling opportunitiesgiven by the DRX wake-up cycle and the DRX Long Cycle, for the casewhere downlink data for the mobile terminal arrives shortly afterentering the DRX Long/wake-up Cycle. As can be appreciated from saidFIG. 12, according to the present disclosure the base station canschedule the mobile terminal shortly after receiving the downlink datausing the wake-up duration of the mobile terminal as an opportunity totransmit a PDCCH DCI format 1 for example. It is of course assumed thatthe base station is not hindered by any other operation (e.g.,scheduling other mobile terminals) and can indeed exploit this wake-upopportunity given by the wake-up duration of one subframe.

In contrast thereto, FIG. 12 alternatively (in dashed lines) depicts thecase where the mobile terminal is scheduled using the on-duration of theDRX long cycle; the base station needs to wait for a longer time to beable to schedule the mobile terminal, and thus the response time for themobile terminal is rather long.

With reference to FIG. 13 a quantitative example is given to compare thefunctioning of the DRX wake-up cycle of one embodiment of the disclosurewith the one of the DRX long cycle. In the example of FIG. 13 it isassumed that the DRX wake-up cycle starts at the same time and inparallel to the DRX long cycle. The DRX wake-up cycle is assumed to be160 subframes, and the DRX long cycle is configured to be 2560subframes; the on-duration is considered to be 4 ms (i.e., 4 subframes),and the wake-up duration is one subframe.

As apparent from FIG. 13 data arrives shortly after the first wake-upduration of the mobile terminal, assumed one subframe after the end ofthe wake-up duration, which can be regarded as being the worst case forthe DRX wake-up cycle. Correspondingly, the base station has to wait atleast 159 subframes (ms) for the first wake-up opportunity given by thesubsequent second wake-up duration. Regarding the DRX long cycle, thebase station would have to wait 2399 subframes (2560-161 subframes) forthe first opportunity to schedule the mobile terminal using theon-duration of the mobile terminal. Accordingly, this is reduction ofthe delay of 2240 ms, or put in other words, only 6.6% of the delay forthe DRX Long cycle.

In a second example downlink data arrives one subframe after thesecond-last wake-up duration, which is the example which yields aminimum gain of 160 ms as follows. According to the DRX wake-up cyclethe downlink scheduling by the base station has to wait 159 ms;considering only DRX long cycle, the base station would have to wait 319ms (160 ms+159 ms) to schedule the mobile terminal.

As already explained above, the reduced response time comes at the costof only marginal additional power consumption, and will be explained inthe following according to the above example of FIG. 13. The worst castscenario with regard to the power consumption is that no data isreceived during the DRX cycle. The mobile terminal has to power up itsRF part for 15 additional subframes to monitor the PDCCH. The DRX longcycle having 2560 ms and a 4 ms on duration, allows a power reduction of99.84% (1-4/2560). In contrast to a mobile terminal also performingaccording to the DRX wake-up cycle, the power reduction is 99.25%(1−19/2560), thus experiencing a power saving loss of only ˜0.59%.

The above considerations however only refer to the theoretical powerconsumption of the mobile terminal. In reality, the mobile terminalsneeds to power up the RF part first, and then power down the RF partafter the wake-up duration (or on-duration for that matter). In otherwords, there is a pre- and post wake-up duration, which lengths aredependent on UE implementation. In one realistic implementation, the prewake-up duration can be assumed to be 5 ms, and the post wake-upduration could be 3 ms. Therefore, the wake-up duration spans 9 ms intotal (5 ms+1 ms+3 ms), and the on-duration spans 12 ms in total (5 ms+4ms+3 ms). Considering these “realistic” power consumption durations, thepower reduction provided by the DRX long cycle alone is 99.53%, and theone for a parallel DRX wake-up cycle is 94.26% (1−(15*9/2560+12/2560)).The DRX wake-up cycle thus yields a power saving loss of 5.26%.

To further asses the advantage provided by the present disclosure, acomparison will be performed between the DRX wake-up cycle and a “short”DRX long cycle with regard to the measurement requirements that are tobe fulfilled by the mobile terminal, and in particular only consideringthe intra and inter-frequency measurements. It is assumed that the DRXlong cycle is 2560 ms long, and the DRX wake-up cycle runs in parallel.On the other hand it is assumed that the DRX long cycle is 160 subframeslong, and the DRX wake-up cycle is not used. As explained before, themeasurement and reporting requirements for the mobile terminal stillfollow the DRX long cycle, and are not influenced or changed by the DRXwake-up cycle which may run parallel to the DRX long cycle. Noadditional subframes for measurements are necessary regarding the DRXwake-up cycle.

Depending on the implementation of the mobile terminal, the subframes ofthe on-duration can be used for intra-cell measurements; thus if theon-duration is more than 5 subframes, no additional subframes are neededfor intra-frequency measurements. In the following, this is however notconsidered for exemplary purposes; the mobile terminal is assumed toperform the intra-frequency measurements on subframes outside theon-duration.

When intra-frequency measurements and the corresponding neighbor cellidentification are assumed to be performed in combination, the mobileterminal is required to spend power on four additional subframes everyDRX cycle, assuming that the on-duration is at least one subframe andcan be used for measurements.

On the other hand, assuming that the previous DRX long cycle was 2560 mslong, if the DRX long cycle is reduced to 160 subframes, to allow thesame response time as with a DRX wake-up cycle of 160 subframes (seeabove), the mobile terminal has to spend 16*4 subframes in 2.56 secondsfor the intra-frequency measurements and cell identification. Thus,there is a difference of 60 subframes which are spent forintra-frequency measurements when reducing the DRX long cycle to 160 ms.

With regard to inter-frequency measurements and corresponding cellidentification, the mobile terminal is required to spend power on 6additional subframes every 2.56 seconds, in case of a DRX long cycle of2560 subframes.

On the other hand, if the DRX long cycle is reduced to 160 subframes,the mobile terminal has to spend 16*6 subframes for inter-frequencymeasurements in 2.56 seconds. This implies 90 additional subframes.

Therefore, only considering intra-frequency and inter-frequencymeasurement requirements, a short DRX long cycle of only 160 subframeswould require 150 additional subframes to perform the necessaryintra/inter-frequency measurements and cell identifications. This meansa penalty of 5.86% (150/2560) for the power consumption of the mobileterminal, only due to complying with the increased measurementrequirements. Put differently, the implementation of the DRX wake-upcycle according to one embodiment of the disclosure allows saving 150subframes that would be necessary for performing the intra-frequency andinter-frequency measurements in case the DRX long cycle is configured tobe 160 subframes. Therefore, instead of using 160 subframes, only 10subframes are necessary when applying the DRX wake-up cycle of 160subframes with a DRX long cycle of 2560 subframes; this means a powerreduction for measurements of 93.75% (150 subframes/160 subframes).

Further assuming an on-duration of 4 ms, and the pre and post wake-upduration of additional 8 ms per on-duration, in 2560 subframes themobile terminal would have to use 1216 subframes for the on-duration and150 subframes for the measurements. Thus, 342 subframes out of the 2560subframes would be spent, and could not be used by the mobile terminalto save power. Thus, the DRX power saving is reduced to only 86.64% inthis case.

In truth, the power saving loss for complying with the requirements formeasurements is higher, since the mobile terminal does not only have toperform the intra-frequency and inter-frequency measurements but othermeasurements as well, such as inter-RAT, CQI, SRS . . . .

It should thus be noted that the requirements for cell measurements aregreatly increased with a short DRX long cycle, which is avoided by thedisclosure.

Similar to the DRX configuration of the prior art, the DRX wake-up cyclecan be configured for the mobile terminal also by the base station,e.g., using RRC messages using the configuration parameters alreadyexplained in above paragraphs. Thus, the eNodeB knows the DRX wake-upcycle of each mobile terminal and can thus use the schedulingopportunities provided by the corresponding wake-up duration subframe(s)to schedule the mobile terminal and/or transmit small data.

One drawback of the embodiments of the disclosure is that the basestation may not have current information on the channel qualityavailable for the mobile terminal, thus making the scheduling by thebase station less efficient since it cannot be based on the currentchannel state. Since the measurement and reporting requirements arelinked to the DRX long cycle and not the DRX wake-up cycle, the mobileterminal correspondingly does neither measure nor report channel qualityinformation to the base station as frequently as might be necessary. Thebase station has the opportunity to send downlink data to the mobileterminal, besides the corresponding PDCCH message for the downlink data,in the subframe of the wake-up duration. Since the base station does notknow the channel state it can preferably use a conservative modulationand coding scheme to compensate for the missing channel qualityinformation and to thus make sure that the downlink data is receivedcorrectly in the mobile terminal. Consequently, the base station canforward small amounts of downlink data with only a small delay to themobile terminal, and this also in the absence of any channel qualityinformation.

Furthermore, the mobile terminal might be configured to measure thechannel and to transmit channel quality information besides the uplinkdata to the base station, in case it gets a DCI format 0 message on thePDCCH. This is particularly useful since the base station otherwiselacks the information of the channel state as just explained above. Themobile terminal would thus perform the necessary measurements on thechannel and would use the uplink grant assigned with the DCI format 0message, to transmit the CQI to the base station. Of course, thisdepends also on whether the UE does have enough time for the channelmeasurements before the uplink grant is due.

Variants

As explained in the background section, several DCI formats aretransmitted on the PDCCH, and the mobile terminal has to perform variousblind decoding attempts to identify these PDCCH messages when monitoringfor the PDCCHs. In the previous embodiments it is assumed that themobile terminal monitors the PDCCH during the wake-up duration in thesame way, as the mobile terminal does for the on-duration; namely, theUE monitors basically all DCI formats, one part in the common searchspace and the other part in the UE-specific search space as explained indetail in the background section.

In the following embodiment of the disclosure, it is assumed that forthe wake-up duration the mobile terminal shall monitor the PDCCH not forall kind of DCI formats, but only for a reduced set thereof. In otherwords, the mobile terminal monitors the PDCCH during the wake-upduration for only pre-determined messages destined to itself.

In one exemplary embodiment of the disclosure, the DCI formats to bemonitored is limited to only DCI formats 0, 1A, 3 and 3A. As apparentfrom the background section, these DCI formats have the same size(namely 42 bits), and thus the mobile terminal needs to perform theblind decoding for only one DCI size, which reduces the number of blinddecoding attempts that the mobile terminal needs to perform. The DCIformats 0, 1A, 3 and 3A allow uplink and downlink scheduling as well asproviding Transmit Power Control commands to the mobile terminal.

Other restrictions with regard to the DCI formats are possible as well.For example, the mobile terminal might be configured to only monitor forone DCI format, e.g., for DCI format 0 thus limiting the mobile terminalto uplink assignments only, or for DCI format 1A, limiting the mobileterminal to downlink assignments only. This has the advantage that themobile terminal needs to be readied only for one type of transmissionwhich is known in advance.

In addition or alternatively, the mobile terminal may ignore all DCIformats that do not contain a code point for indicating a CQI-onlyassignment. A code point for CQI-only tells the mobile terminal that itshould perform channel measurements and report the CQI to the basestation without informing the MAC layer of either reception ortransmission of a transport block. The mobile terminal will use acontrol channel (PUCCH) for sending the CQI to the base station since noother uplink resource was provided to the mobile terminal Thus, the basestation can specifically request a CQI from the mobile terminal,particularly in those cases where downlink data is to be transmitted tothe mobile terminal and the base station wants to first learn thechannel state before forwarding the data to the UE. However, the step offirst requesting the UE to perform measurements and report the CQIintroduces an additional delay of ˜6 ms-8 ms for forwarding the downlinkdata to the mobile terminal.

However, this 6-8 ms delay corresponds roughly to the time necessary foran SCell to wake up. Thus, this delay may not be detrimental for thosecases where the SCell is involved.

In another embodiment of the disclosure the aggregation levels that themobile terminal is to monitor for PDCCH is limited. As explained in thebackground section, the PDCCH format defines the number of CCEs that areused for transmitting the PDCCHs; either 1, 2, 4 or 8 CCEs may be used,e.g., depending on the channel conditions (8 CCEs is most robust, 1 CCEis least robust). However, when the PDCCH is transmitted using a lownumber of CCEs this forces the mobile terminal to perform a lot of blinddecoding to scan the search space for the PDCCH message.Correspondingly, in order to limit the effort by the UE for blinddecoding the PDCCH format to be monitored can be limited, e.g., to justPDCCH formats 2 and 3, meaning 4 and 8 CCEs are used only, or to justPDCCH format 3, meaning that messages with 8 CCEs are to be checkedonly.

A further option to reduce the blind decoding attempts at the mobileterminal, is to limit the monitoring of the PDCCH to only the commonsearch space or the mobile terminal specific search space.

The above embodiments of limiting the monitoring of PDCCH, with regardto a reduced set of DCI formats, predetermined PDCCH formats and one ofthe search spaces, can be combined as well to further reduce the powerspent by the UE on blind decoding.

When introducing the DRX wake-up cycle, there will be several mobileterminals monitoring the PDCCH during a given subframe. In view of thatthe probability of false alarm in LTE is just found acceptable, reducingthe blind decoding attempts according to one or a combination of theabove embodiments helps reducing the false alarm rate further.

For the following it is assumed that carrier aggregation is applied forthe UE, such that it has a primary cell (PCell) and one or severalsecondary cells (SCell). The DRX operation according to the prior art isvalid for the complete UE, thus for the PCell and any other (activated)SCell(s). Correspondingly, the UE would operate according to the DRXshort/long cycle in each PCell, SCell separately and would monitor thePDCCH of the PCell and the one of each SCell according to the currentlyactive DRX cycle.

In one embodiment of the present disclosure, the operation of the DRXwake-up cycle can be the same in the PCell as in any of the SCells; thismeans that the mobile terminal not only performs the DRX wake-up cycle,according to one of the above described embodiments, in the PCell butalso in each of the SCells.

According to another embodiment of the disclosure, the UE may however beconfigured such that the DRX wake-up cycle is only performed in thePCell but not in any of the SCell(s); the DRX short/long cycle wouldstill be applied for the SCell, however the DRX wake-up cycle operationnot. In other words, during the DRX wake-up duration the mobile terminalonly monitors the PDCCH on the PCell.

This is illustrated using FIG. 14, which depicts the PCell and oneSCell. As apparent therefrom, the operation of the DRX short/long cycleis the same on the PCell and the SCell and is not different from theoperation according to the prior art. On the other hand, it can beappreciated from FIG. 14 that according to the present embodiment of thedisclosure, the UE operates according to the DRX wake-up cycle only onthe PCell, according to one of the previous embodiments of thedisclosure; in this case for example, it starts the DRX wake-up cyclewith the DRX long cycle and without any offset.

This allows saving further power since the UE does not need to monitorfor PDCCHs on the SCell. This makes especially sense in case the SCellis on another frequency (with interband aggregation) since the radiohead (radio frequency part) of the mobile terminal can thus be turnedoff for the SCell.

Cross-carrier scheduling allows the PDCCH of a component carrier toschedule resources on another component carrier. For this purpose acomponent carrier identification field is introduced in the respectiveDCI formats, called CIF. However, cross carrier scheduling might not besupported when the DRX wake-up cycle is only implemented in the PCell,since the SCell requires a wake-up period to be able to decode messages.

This is depicted in FIG. 15, displaying the SCell wake-up time necessaryafter receiving a corresponding PDCCH message on the PCell. The SCellcan be ready for scheduling after ˜8 ms (similar to the time necessaryfor activating a previously deactivated SCell).

Therefore, in case a scheduling message for the SCell is received on thePDCCH on the PCell, the downlink data on the same subframe of the SCellcan not be decoded by the UE. In case an uplink scheduling message forthe SCell is received on the PDCCH on the PCell, the UE might still nothave enough time to wake-up the SCell in time to prepare and send theuplink data via the SCell.

Correspondingly, in one embodiment of the disclosure the mobile terminalignores cross scheduling messages, i.e., PDCCH messages with the carrierindicator pointing to one of the SCells.

According to still another embodiment of the disclosure, the mobileterminal does not monitor the complete cell bandwidth of a cell whenmonitoring the PDCCH during the wake-up duration of the DRX wake-upcycle, but restricts the monitoring to only part of the cell bandwidth.Assuming that the cell has an frequency bandwidth of 5 MHz, it has beenassumed before that the mobile terminal does also receive the cell overits complete bandwidth of 5 MHz, when monitoring for PDCCHs using all ofthe available 5 MHz. However, in order to further save battery power,the mobile terminal may only monitor part of the cell bandwidth, e.g.,1.4 MHz around the center frequency of the subband. Usually, the SystemInformation is transmitted in the 1.4 MHz subband around the centerfrequency.

The eNodeB of course needs to transmit messages to the mobile terminalin this reduced frequency subband of 1.4 MHz so that the mobile terminalis able to decode the messages when monitoring the PDCCH.

Furthermore, when the frequency bandwidth is limited as explained above,the eNodeB might send an Active Bandwidth Indicator to the mobileterminal in this limited frequency bandwidth. When the mobile terminaldetects the Active Bandwidth Indicator, it returns the receptionbandwidth to the regular cell bandwidth of, e.g., 5 MHz. Therefore, infuture occurrences of the wake-up durations of the DRX wake-up cycle,the UE monitors the complete frequency bandwidth. Alternatively, theActive Bandwidth Indicator can be understood by the UE as a trigger toenter Active Time.

A further embodiment of the disclosure relates to limiting theoccurrences of the DRX wake-up duration, as will be explained in moredetail below. For example smartphones run several applications at thesame time, while not actively using them. The applications receivekeep-alive packets in order to maintain connectivity with the network.These keep-alive packets may arrive with a “combined” periodicity and aparticular variance around this periodicity. The exact determination ofthe arrival of the keep-alive packets is difficult, and such a packetshall not be delayed until the next on duration of the DRX long cycle.Usually, the DRX long Cycle is configured such that the DRX on-durationsare placed at the expected arrivals of the keep-alive packets.

While the UE can assist the eNodeB to adapt the DRX long cycle withstatistics information regarding the keep-alive packets arrival, itwould be advantageous to also allow for the variance of the keep-alivepackets. The active time of the UE and the DRX short cycle are notenough since they can take only care of packets arriving when a firstpacket was received in the on-duration during the DRX long cycle.

According to another embodiment of the disclosure, the DRX wake-up cycleis thus configured such that the UE operates according to the DRXwake-up cycle for only a limited amount of time; the occurrences of thewake-up duration of the DRX wake-up cycle are thus reduced.

According to one implementation of this embodiment, a wake-up durationenable timer is started when the DRX wake-up cycle starts. The UEmonitors the PDCCH for the wake-up duration according to the timeintervals given by the DRX wake-up cycle only when the wake-up durationenable timer is running. When the wake-up duration enable timer expires,the UE does not monitor the PDCCH even if it would according to the DRXwake-up cycle. The wake-up duration enable timer is reset every time theUE exists the Active Time of the on-duration of the DRX long cycle. Thisallows to only have occurrences of the DRX wake-up duration for alimited amount of time after the on-durations of the DRX long cycle.

This will be explained with reference to FIG. 16, which illustrates thewake-up duration enable timer running after the end of the on-durationof the DRX long cycle. As in previous embodiments of the disclosure, theDRX wake-up cycle is assumed to start at the same time as the DRX longcycle. With start of the DRX wake-up cycle the wake-up duration enabletimer is started too for the first time. The UE operates according tothe DRX wake-up cycle as explained before, as long as the wake-upduration enable timer is still running. Correspondingly, every time thewake-up duration of the DRX wake-up cycle is imminent (i.e., the mobileterminal is due to monitor the PDCCH), the UE first checks the wake-upduration enable timer as to whether same is still running or whether ithas already expired. The mobile terminal only monitors the PDCCH for thewake-up duration of time (as explained in previous embodiments) in casethe wake-up duration enable timer is still running, i.e., has not yetexpired. Otherwise, the UE will not monitor the PDCCH for the wake-upduration even if it would have to according to the DRX wake-up cycle. InFIG. 16 this yields that the mobile terminal only performs the PDCCHmonitoring for two occurrences (instead of four) after the on-durationof the DRX long cycle.

Thus, in case keep-alive packets unexpectedly arrive after the expectedtime (during the on-duration), the DRX wake-up cycle allows furtherscheduling opportunities for the base station to forward the keep-alivepackets to the mobile terminal. At the same time, the mobile terminaldoes not have to monitor the PDCCH for all wake-up opportunities of thewake-up duration, which saves further power.

Alternatively or in combination with the above, instead of havingwake-up duration occurrences limited to only after the on-durations ofthe DRX long cycle, another embodiment allows to limit the wake-upduration occurrences to only before the on-durations of the DRX longcycle. Correspondingly, instead (or in addition) to the wake-up durationenable timer, a wake-up duration prohibition timer is implemented in theUE such that the UE only monitors the PDCCH for the wake-up duration oftime according to the DRX wake-up cycle, when the wake-up durationprohibition timer is not running.

This is illustrated in FIG. 17, where only two occurrences of thewake-up durations are depicted before the on-durations; the mobileterminal actually monitors the PDCCH only two times, since the first twowake-up opportunities are not used due to the running wake-up durationprohibition timer. In correspondence to the wake-up duration enabletimer before, the wake-up duration prohibition timer is reset uponexpiry of the on-duration of the DRX long cycle, upon exiting ActiveTime.

By using one or both of the timers explained above, it is possible toflexibly configure the DRX wake-up cycle so as to adapt to thecircumstances and needs of the mobile terminal and at the same time toavoid waste of battery power for wake-up durations where no downlinkpacket is to be received.

Further Embodiments

In further embodiments, the mobile terminal monitors the PDCCH duringthe paging occasions while being in DRX of RRC_CONNECTED state, as willbe explained below.

In the current specification, the UE can monitor paging occasions alsowhen being in the RRC_CONNECTED state, in order to be informed aboutSystem Information changes. The paging occasions occur more frequentlythan the on-durations in a DRX long cycle.

According to a further embodiment, the UE being in DRX long cycle maymonitor the PDCCH for messages during the paging occasions. For saidpurpose a wake-up RNTI (WU-RNTI) is introduced, such that when a PDCCHmessage is scrambled with the WU-RNTI, this would instruct the UE towake-up. As with the P-RNTI, there is only WU-RNTI for the mobileterminal in the system.

The paging and the wake-up mechanism is thus separated, which avoidsunnecessary reception of the paging or wake-up message.

In the wake-up message transmitted in the paging occasion, awakeUpRecordList is added, similar to the normal paging message. The UEbeing in the DRX long cycle reads this wakeUpRecordList, and if it findits identity (C-RNTI), it wakes up from DRX.

This is illustrated in FIG. 18, illustrating various paging occasions,one of which is used by the eNodeB to transmit a PDCCH message using theWU-RNTI, after downlink data arrives for the UE. Correspondingly, the UEmonitors the PDCCH for this message, decodes same and due to the WU-RNTIlearns that it shall wake-up. After a defined time of subframes afterthe paging occurrence, the UE returns to Active Time and could, e.g., bescheduled. This gap is necessary to provide time for the paging messagereception; at least 4 subframes; may also allow for 8 subframes, similarto the SCell activation. In this time the mobile terminal can receivethe wake-up message from the eNodeB, which CRC is scrambled now with theC-RNTI of the mobile terminal. At the beginning of the procedure it isnot possible for the mobile terminal to receive a data transmission,only the wake-up message.

The mobile terminal can thus be woken up by the eNodeB earlier than ifonly using the DRX long cycle. The exemplary difference is depicted inFIG. 18 using dashed lines. Furthermore, by reusing the paging mechanismthe mobile terminal only needs to blindly decode one RNTI (besides thesearching for the System Information change).

Alternatively, instead of monitoring the paging occasion for the WU-RNTIthe mobile terminal can monitor the paging occasion for a PDCCH messagemasked with another RNTI assigned directly to the mobile terminal. Thisallows for a faster procedure for waking up the mobile terminal as nofurther checks as described above have to be performed as the RNTI isalready specific to the mobile terminal. This alternative comes with thedrawback of increasing PDCCHs during the paging occasion.

In another embodiment of the disclosure, the eNodeB configures themobile terminal with persistent downlink assignments (SPS,semi-persistent scheduling), where the intervals is several timesshorter than the DRX long cycle. SPS is activated during the ActiveTime. During DRX, the UE shall receive the PDSCH on configuredassignments, and decodes the transport block of these configuredassignments.

In case the decoding of the transport block at the configured assignmentfails, no HARQ operation is to be performed, and consequently, themobile terminal does not wake up for re-transmissions (HARQ RTT notstarted). On the other hand, if the decoding of the transport block issuccessful, the mobile terminal returns to Active Time. It should benoted that a gap might become necessary to provide time for thetransport block to be successfully decoded, before the UE can actuallyenter Active Time.

The benefit of this embodiment is that it is implementation friendlysince only changes to the SPS operation during DRX are required.However, there may be a delay between the configured assignment and thestart of the Active Time. Also, additional signaling might be necessary,if SPS needs to be activated/deactivated before/after the DRX phase.Further, if SPS stay active during the Active Time, this would lead to awaste of downlink resources. FIG. 19 depicts the functioning of thisembodiment of the disclosure.

Mobile terminals, and in particular smartphones create traffic frommultiple application being active in the mobile terminal at the sametime. Such a mix of application creates data traffic which is hard topredict. This is especially true on the RAN level, where the downlinkdata arriving in the eNodeB cannot be correlated with a specificapplication. Furthermore, applications have different delayrequirements.

The network is in control of putting the mobile terminal in a state withmore power saving (e.g., RRC_IDLE) or to keep the mobile terminal inactive state. Correspondingly, the network has to weigh the mobileterminal's power consumption against the network's signaling load andbasically has two choices. At the cost of higher signaling load for thestate transition and an increased delay, the mobile terminal's powersaving is enhanced. At the cost of higher power consumption in themobile terminal, network refrains from state transmission and thecorresponding signaling thus reducing the signaling overhead, and avoidsthe delay introduced by being in idle.

Therefore, there is the problem that due to the unknown traffic patternat network side, the mobile terminal is kept in active state longer thanwould be necessary; this is unnecessary from the mobile terminal's pointof view, and wastes the mobile terminal's battery.

As explained in the background section Fast Dormancy was introduced byRelease 8 of LTE.

One embodiment of the disclosure solves this problem differently. The UEindeed has knowledge of the applications it is running, and thus mayconclude from the active application, the expected datareception/transmission behavior on RAN layer. Therefore, the UE maypredict the downlink traffic pattern, it will be scheduled with from theeNodeB.

The UE indicates the expected end of the downlink data to the eNodeB, inresponse to which the eNodeB may send a DRX MAC CE to the mobileterminal in order for the mobile terminal to enter the DRX mode. Thisavoids signaling overhead as the UE is kept in active state. A goodpower efficiency is achieved by the configuring the short and long DRXcycles appropriately. For example, the short DRX cycle may be configuredto match the actual traffic, and the long DRX cycle may model the idlemode. The short and long DRX cycles may also be extended to cycleperiods longer than currently allowed in the standardization (current640 ms and 2560 ms, respectively), so as to achieve higher powerefficiency.

According to a further embodiment of the disclosure, the eNodeB mayindicate to the UE to directly operate according to the Long DRX cyclewithout operating according the Short DRX cycle first, in order tofurther save batter power in the UE. This could be implemented forexample by changing the MAC DRX CE to not only include the command for“go-to-sleep” but also the indication of “immediate transition fromshort to long DRX cycle”.

The indication of the expected end of the downlink data to the eNodeBcan be implemented according to one of the following.

The indication could be done via RRC signaling, like in HSPA fastdormancy. Alternatively, a new MAC control element could be defined,using one of the currently reserved LCIDs; no payload is thus necessaryfor indicating the expected end of the downlink data. Or, the indicationcan be inserted into the Buffer Status Report (BSR).

In the MAC header for the short and/or long BSR, one of the reservedbits is used to indicate that the UE expects the end of downlink data.In this case, the indication will only be sent if a BSR is triggered;thus, the triggering rule may need to be changed.

A further alternative embodiment relates to sending the indication inthe CQI report. When the UE is configured with periodic CQI reporting,the mobile terminal can set an “out of range” value, when reporting,e.g., the wideband CQI.

Furthermore, in one embodiment the measurements on the activated SCellsdo not follow the DRX long cycle but the parameter measCycleSCellusually employed for deactivated SCells. The measCycleSCell isconfigurable to 160, 256, 320, 512, 640, 1024 and 1280 subframes. The UEis configured to measure once within 5 times the measCycleSCell. Thisallows further relaxed measurement requirements for the UE with furtherpower saving.

Hardware and Software Implementation of the Disclosure

Another embodiment of the disclosure relates to the implementation ofthe above described various embodiments using hardware and software. Inthis connection the disclosure provides a user equipment (mobileterminal) and a eNodeB (base station). The user equipment is adapted toperform the methods described herein. Furthermore, the eNodeB comprisesmeans that enable the eNodeB to evaluate the IPMI set quality ofrespective user equipments from the IPMI set quality informationreceived from the user equipments and to consider the IPMI set qualityof the different user equipments in the scheduling of the different userequipments by its scheduler.

It is further recognized that the various embodiments of the disclosuremay be implemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of thedisclosure may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the disclosure may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

It should be further noted that the individual features of the differentembodiments of the disclosure may individually or in arbitrarycombination be subject matter to another disclosure.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present disclosure asshown in the specific embodiments without departing from the spirit orscope of the disclosure as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

The invention claimed is:
 1. A method of discontinuous reception (DRX)for a mobile terminal being in communication with a base station in amobile communication system, the method comprising: configuring a shortdiscontinuous reception (DRX) cycle and a DRX short cycle timeraccording to a first configuration that defines the short DRX cycle, anda long DRX cycle according to a second configuration that defines thelong DRX cycle, in response to receiving, from the base station, a firstDRX command MAC (Medium Access Control) control element, starting theDRX short cycle timer and starting using the short DRX cycle, andstarting using the long DRX cycle after the DRX short cycle timerexpires, and in response to receiving, from the base station, a secondDRX command MAC control element, which is different from the first DRXMAC control element and includes an indication of the long DRX cycle,stopping the DRX short cycle timer and starting using the long DRXcycle.
 2. The method according to claim 1, wherein the second DRXcommand MAC control element including the indication of the long DRXcycle is transmitted from the base station when the base station expectsend of downlink data for the mobile terminal.
 3. The method according toclaim 2, wherein the mobile terminal indicates the expected end of thedownlink data to the base station.
 4. The method according to claim 1,further comprising: receiving a third configuration that defines anadditional DRX cycle from the base station, starting using theadditional DRX cycle in parallel to using the short or long DRX cycle,and monitoring a downlink control channel for messages destined to themobile terminal for a particular duration of time.
 5. The methodaccording to claim 1, further comprising: repeating using the long DRXcycle until a scheduling message is received from the base station. 6.The method according to claim 1, further comprising: monitoring aphysical downlink control channel (PDCCH) by discontinuously using theshort DRX cycle and the long DRX cycle.
 7. A mobile terminal forperforming discontinuous reception (DRX) in communication with a basestation in a mobile communication system, the mobile terminalcomprising: a processor which, in operation, configures a shortdiscontinuous reception (DRX) cycle and a DRX short cycle timeraccording to a first configuration that defines the short DRX cycle, andconfigures a long DRX cycle according to a second configuration thatdefines the long DRX cycle, and a receiver coupled to the processor,wherein, when the receiver receives from the base station a first DRXcommand MAC (Medium Access Control) control element, the processorstarts the DRX short cycle timer and starts using the short DRX cycle,and starts using the long DRX cycle after the DRX short cycle timerexpires, and wherein, when the receiver receives from the base station asecond DRX command MAC control element, which is different from thefirst DRX MAC control element and includes an indication of the long DRXcycle, the processor stops the DRX short cycle timer and starts usingthe long DRX cycle.
 8. The mobile terminal according to claim 7, whereinthe receiver receives the second DRX command MAC control elementincluding the indication of the long DRX cycle from the base stationwhen the base station expects end of downlink data for the mobileterminal, and wherein a transmitter of the mobile terminal, inoperation, indicates the expected end of the downlink data to the basestation.
 9. The mobile terminal according to claim 7, wherein, when thereceiver receives a third configuration that defines an additional DRXcycle from the base station, the processor starts using the additionalDRX cycle in parallel to using the short or long DRX cycle, and monitorsa downlink control channel for messages destined to the mobile terminalfor a particular duration of time.
 10. The mobile terminal according toclaim 7, wherein the processor repeats using the long DRX cycle untilthe receiver receives a scheduling message from the base station. 11.The mobile terminal according to claim 7, wherein the receiver and theprocessor monitor a physical downlink control channel (PDCCH) bydiscontinuously using the short DRX cycle and the long DRX cycle.